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Until recently hamburgers at the city sports arena cost \(\$ 4\) each. The food concessionaire sold an average of 10,000 hamburgers on a game night. When the price was raised to \(\$ 4.40,\) hamburger sales dropped oft to an average of 8000 per night. (a) Assuming a linear demand curve, find the price of a hamburger that will maximize the nightly hamburger revenue. (b) If the concessionaire has fixed costs of \(\$ 1000\) per night and the variable cost is \(\$ .60\) per hamburger, find the price of a hamburger that will maximize the nightly hamburger profit.

Short Answer

Expert verified
Revenue-maximizing price: \(\$3\). Profit-maximizing price: \(\$3.30\).

Step by step solution

01

- Define Variables and Linear Demand Equation

Let the price of a hamburger be denoted by p and the quantity sold by q. Given two points on the demand curve: (4, 10000) and (4.40, 8000). Use the slope formula to find the slope (m) of the demand curve: \[ m = \frac{8000 - 10000}{4.40 - 4} = -5000 \] The demand equation is linear: \[ q = mp + b \] Substitute one of the points to find b: \[ 10000 = -5000(4) + b \] solving this gives \[ b = 30000 \] Therefore, the linear demand function is: \[ q = -5000p + 30000 \]
02

- Revenue Function

Revenue is given by R(p) = p * q. Substituting the demand function: \[ R(p) = p(-5000p + 30000) = -5000p^2 + 30000p \]
03

- Maximize Revenue

To find the price that maximizes revenue, take the derivative of R(p) with respect to p and set it to zero: \[ R'(p) = -10000p + 30000 \] Setting R'(p) = 0: \[ -10000p + 30000 = 0 \] Solving for p gives: \[ p = 3 \]
04

- Profit Function

Profit is given by Profit = Revenue - Costs. Where \( \text{Total Cost} = \text{Fixed Cost} + \text{Variable Cost} \). Let’s define variable (VC) and fixed costs (FC): VC = 0.60q, FC = 1000. Therefore, Cost(p) = 1000 + 0.60q. Using the demand function to substitute q in Cost(p): \[ \text{Cost}(p) = 1000 + 0.60(-5000p + 30000) = 1000 - 3000p + 18000 = -3000p + 19000 \]
05

- Maximize Profit

Profit(p) = Revenue(p) - Cost(p), substituting in values from earlier: \[ \text{Profit}(p) = (-5000p^2 + 30000p) - (-3000p + 19000) \] Simplifying gives: \[ \text{Profit}(p) = -5000p^2 + 33000p - 19000 \] Take the derivative of Profit(p) and set it to zero to find p that maximizes profit. \[ \text{Profit}'(p) = -10000p + 33000 \] Setting \(\text{Profit}'(p) = 0 \): \[ -10000p + 33000 = 0 \] Solving for p gives: \[ p = 3.30 \]

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Key Concepts

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

linear demand curve
A linear demand curve shows the relationship between price and quantity in a straight line. Imagine two points: (4, 10000) and (4.40, 8000). The first point means that at \(4 per hamburger, 10,000 hamburgers were sold. The second indicates a reduced sale of 8,000 hamburgers when the price increased to \)4.40. We use the slope formula to find the rate of decrease:
  • Slope = \[\frac{8000 - 10000}{4.40-4} = -5000\]
This gives us a negative slope, meaning an inverse relationship between price and quantity. The linear demand equation can be specified as: \[q = -5000p + b\]. Using either point, we substitute p and q to find b: \[10000 = -5000(4) + b\]. Solving, we get b = 30000. Therefore, our demand curve is: \[q = -5000p + 30000\].
revenue function
Revenue function highlights the total income received from selling goods. Calculate it by multiplying the price per unit (p) by the quantity sold (q). With our demand curve \[q = -5000p + 30000\], the revenue formula becomes: \[R(p) = p \times q = p(-5000p + 30000)\]. Further simplifying: \[R(p) = -5000p^2 + 30000p\].
profit function
The profit function is essential for understanding earnings after costs. Profit = Revenue - Costs. Costs have two components: Fixed Costs (FC) and Variable Costs (VC). Given fixed costs of $1000 and variable costs of 0.60 per hamburger, total cost = \[1000 + 0.60q\]. Using \[q = -5000p + 30000\] to find q: \[Cost(p) = 1000 + 0.60(-5000p + 30000) = 1000 - 3000p + 18000\]. Simplifying gives: \[-3000p + 19000\]. Profit is thus: \[Profit = Revenue - Cost = (-5000p^2 + 30000p) - (-3000p + 19000) = -5000p^2 + 33000p - 19000\].
slope formula
The slope formula \[m = \frac{y2 - y1}{x2 - x1}\] calculates the rate of change between two points. Given points (4, 10000) and (4.40, 8000), the slope is: \[-5000 = \frac{8000 - 10000}{4.40 - 4}\]. This slope is crucial for forming the linear demand curve to understand how quantity changes with price.
derivative in calculus
A derivative helps find the rate of change. To maximize revenue or profit, we take the derivative of the respective function and set it to zero:
  • For Revenue: \[R(p) = -5000p^2 + 30000p\], derivative: \[R'(p) = -10000p + 30000\]. Solving \[R' = 0\]: \[p = 3\].
  • For Profit: \[Profit = -5000p^2 + 33000p - 19000\], derivative: \[Profit'(p) = -10000p + 33000\]. Solving \[Profit' = 0\]: \[p = 3.30\].
These steps tell us the optimal price points to maximize revenue and profit respectively.

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