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You are given a linear programming problem. a. Use the method of corners to solve the problem. b. Find the range of values that the coefficient of \(x\) can assume without changing the optimal solution. c. Find the range of values that resource 1 (requirement 1) can assume. d. Find the shadow price for resource 1 (requirement 1). e. Identify the binding and nonbinding constraints. $$ \begin{array}{cc} \text { Minimize } & C=2 x+5 y \\ \text { subject to } & x+2 y \geq 4 \\ & x+y \geq 3 \\ & x \geq 0, y \geq 0 \end{array} $$

Short Answer

Expert verified
In summary: a. The optimal solution using the method of corners is (3, 0) with a minimum cost of \(C = 6\). b. The range of values that the coefficient of \(x\) can assume without changing the optimal solution is \(\frac{4}{3} < a < 2\). c. The range of values that resource 1 (requirement 1) can assume is \(k \geq 3\). d. The shadow price for resource 1 (requirement 1) is 0. e. Binding constraint: \(x+y\geq3\), Nonbinding constraint: \(x+2y\geq4\)

Step by step solution

01

Rewrite the inequalities as equations

We need to find the corner points of the feasible region. First, let's rewrite the inequalities as equations: $$ x+2y = 4 \\ x+y = 3 \\ x = 0, y = 0 $$
02

Find the corner points of the feasible region

Now we'll find the intersection points of the lines derived from the inequalities, and these will be our corner points of the feasible region. We have four possible intersections: (1) Between the first and second lines, (2) between the first line and x-axis, (3) between the second line and x-axis, and (4) between the second line and y-axis. Intersection of the first and second lines: $$ \begin{cases} x + 2y = 4 \\ x + y = 3 \\ \end{cases} $$ Solving these equations, we get the point (1, 2). Intersection of the first line and x-axis: $$ \begin{cases} x + 2y = 4 \\ x = 0 \\ \end{cases} $$ Solving these equations, we get the point (0, 2). Intersection of the second line and x-axis: $$ \begin{cases} x + y = 3 \\ x = 0 \\ \end{cases} $$ Solving these equations, we get the point (0, 3). Intersection of the second line and y-axis: $$ \begin{cases} x + y = 3 \\ y = 0 \\ \end{cases} $$ Solving these equations, we get the point (3, 0).
03

Substitute corner points into the objective function

Now, we will substitute these corner points into our objective function \(C = 2x + 5y\) and find the minimum value: $$ C(1, 2) = 2(1) + 5(2) = 12 \\ C(0, 2) = 2(0) + 5(2) = 10 \\ C(0, 3) = 2(0) + 5(3) = 15 \\ C(3, 0) = 2(3) + 5(0) = 6 $$ The minimum value of C occurs at the point (3, 0) with the value of 6. a. The optimal solution using the method of corners is (3, 0) with a minimum cost of \(C = 6\). We will now address the other parts of the problem: b. The optimal solution occurs at the intersection of the second line (\(x+y \geq 3\)) and the x-axis. The range of values for the coefficient of \(x\) in the objective function, such that it doesn't change the optimal solution, is when the second constraint remains binding. To keep it binding, we must ensure that changing the coefficient of \(x\) does not make the first constraint become the new binding constraint. Therefore, we must ensure that the slope of the objective function, \(-\frac{2}{5}\), remains between the slopes of the first two constraints, which are \(-\frac{1}{2}\) and \(-1\): $$ -1 < -\frac{2}{a} < -\frac{1}{2} $$ Solving for \(a\), we get \(\frac{4}{3} < a < 2\). b. The range of values that the coefficient of \(x\) can assume without changing the optimal solution is \(\frac{4}{3} < a < 2\). c. Resource 1 (requirement 1) corresponds to the first constraint, \(x + 2y \geq 4\). To find the range of values it can assume without affecting the optimal solution, we'll consider the constraint as \(x + 2y \geq k\) and observe that the intersection of this constraint and the second constraint remains at the optimal point (3, 0): $$ (3) + 2(0) \geq k $$ k can be as low as 3, but there is no upper bound. c. The range of values that resource 1 (requirement 1) can assume is \(k \geq 3\). d. The shadow price for resource 1 (requirement 1) is the change in the objective function when the constraint is increased by one unit. Since the range for resource 1 showed no upper bound, resource 1 doesn't affect the optimal solution, and its shadow price is 0. d. The shadow price for resource 1 (requirement 1) is 0. e. To identify binding and nonbinding constraints, we can observe how the constraints affect the optimal solution. A constraint is binding if it affects the optimal solution. The second constraint (\(x+y\geq3\)) is binding, as it determines the optimal solution. The first constraint (\(x+2y\geq4\)) is nonbinding, as it doesn't affect the optimal solution. e. Binding constraint: \(x+y\geq3\), Nonbinding constraint: \(x+2y\geq4\)

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Method of Corners
Understanding the Method of Corners is crucial when solving linear programming problems. This method is used to find the optimal solution by exploring the vertices (or 'corners') of the feasible region in a graphical solution space. In a linear programming problem, the feasible region is the set of all possible points that satisfy all the given constraints, including the non-negativity constraints.
Within the context of our exercise, the feasible region is determined by the constraints that include two inequalities and the requirement that both variables, in this case, x and y, must be greater than or equal to zero. By rewriting the inequalities as equations, we obtain lines that bound this region. The intersections of these lines, along with the axes, create the corners of the feasible region.
After finding the corner points, which we have mathematically determined in our step-by-step solution, we then evaluate the objective function, in this case, the cost function C, at each corner to identify which gives us the minimum value. The point with the lowest cost is our optimal solution. For the exercise provided, substituting the corner points into the cost function revealed that the point (3, 0) is optimal, giving us the minimum cost of C = 6.
The method of corners is particularly efficient because it leverages the fact that in a linear programming problem with two variables, the optimal solution always lies at one of the corners. This direct approach allows students to visually and algebraically find the solution without exhaustive calculations.
Binding and Nonbinding Constraints
In the realm of linear programming, constraints play a critical role in forming the feasible region for a solution. They can either be 'binding' or 'nonbinding'. Understanding the difference between these two kinds of constraints is key to grasping the intricacies of linear programming.
A constraint is considered binding if changing it would affect the optimal solution of the problem. In other words, these constraints are 'tight' because the optimal solution lies exactly on the boundary they form. In contrast, a constraint is nonbinding if it does not affect the determination of the optimal solution; you can change this constraint without changing the optimal point of the problem.
To put this into the context of our example, we have the following constraints for the linear programming problem: x + 2y ≥ 4 and x + y ≥ 3. From the step-by-step analysis, it was determined that x + y ≥ 3 is a binding constraint as it dictates the optimal solution. Any change to this inequality can move the optimal solution to a different corner of the feasible region. The other inequality, x + 2y ≥ 4, is nonbinding because the optimal solution would remain unchanged if this inequality is altered, provided it doesn't intersect the feasible region elsewhere.
The recognition of binding constraints is not merely an academic exercise; it has practical implications. For instance, if a constraint is binding, altering its parameters could potentially improve or degrade the objective function value. Conversely, nonbinding constraints offer a degree of flexibility because they do not impact the optimal solution directly.
Shadow Price
The shadow price is an economic concept within linear programming that represents the rate of improvement in the objective function value as a function of the right-hand side of a constraint. It is an invaluable aspect of sensitivity analysis, as it helps us understand how much one additional unit of a resource would affect the optimal cost or profit.
In our exercise, we look at the shadow price for resource 1 (requirement 1), represented as the first constraint (x + 2y ≥ 4). Understanding the shadow price involves evaluating how changes to this constraint's resources would alter the objective function — in this case, the cost. The shadow price generally carries a value if the constraint is binding; however, if the constraint is nonbinding or the range of possible variation is very large (or infinite), the shadow price can be zero.
Based on our calculations, the shadow price for resource 1 is determined to be 0. This is because the constraint is nonbinding, and therefore, adjustments to resource 1's availability do not change the minimum cost outcome. This insight can assist decision-makers in prioritizing resource allocation or identifying the worth of acquiring additional units of a resource. In production settings, for example, knowing the shadow price helps in understanding whether investing in more of a certain resource could lead to increased profits or reduced costs.

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Most popular questions from this chapter

NUTRITION-DIET PLANNING A nutritionist at the Medical Center has been asked to prepare a special diet for certain patients. She has decided that the meals should contain a minimum of \(400 \mathrm{mg}\) of calcium, \(10 \mathrm{mg}\) of iron, and \(40 \mathrm{mg}\) of vitamin \(\mathrm{C}\). She has further decided that the meals are to be prepared from foods \(A\) and \(B\). Each ounce of food \(A\) contains \(30 \mathrm{mg}\) of calcium, \(1 \mathrm{mg}\) of iron, \(2 \mathrm{mg}\) of vitamin \(\mathrm{C}\), and \(2 \mathrm{mg}\) of cholesterol. Each ounce of food \(\mathrm{B}\) contains \(25 \mathrm{mg}\) of calcium, \(0.5 \mathrm{mg}\) of iron, \(5 \mathrm{mg}\) of vitamin \(\mathrm{C}\), and \(5 \mathrm{mg}\) of cholesterol. Find how many ounces of each type of food should be used in a meal so that the cholesterol content is minimized and the minimum requirements of calcium, iron, and vitamin \(\mathrm{C}\) are met.

Solve each linear programming problem by the method of corners. $$ \begin{array}{rc} \text { Minimize } & C=3 x+6 y \\ \text { subject to } & x+2 y \geq 40 \\ & x+y \geq 30 \\ & x \geq 0, y \geq 0 \end{array} $$

Determine graphically the solution set for each system of inequalities and indicate whether the solution set is bounded or unbounded. $$ \begin{array}{r} x+2 y \geq 3 \\ 2 x+4 y \leq-2 \end{array} $$

Determine whether the statement is true or false. If it is true, explain why it is true. If it is false, give an example to show why it is false. The problem $$ \begin{aligned} \text { Minimize } & C=2 x+3 y \\ \text { subject to } & 2 x+3 y \leq 6 \\ & x-y=0 \\ & x \geq 0, y \geq 0 \end{aligned} $$ is a linear programming problem.

You are given a linear programming problem. a. Use the method of corners to solve the problem. b. Find the range of values that the coefficient of \(x\) can assume without changing the optimal solution. c. Find the range of values that resource 1 (requirement 1) can assume. d. Find the shadow price for resource 1 (requirement 1). e. Identify the binding and nonbinding constraints. $$ \begin{array}{ll} \text { Maximize } & P=2 x+5 y \\ \text { subject to } & x+3 y \leq 15 \\ & 4 x+y \leq 16 \\ & x \geq 0, y \geq 0 \end{array} $$

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