A model for consumers' response to advertising is given by \(N(a)=1000+200 \ln
a, \quad a \geq 1\)
where \(N(a)\) is the number of units sold and \(a\) is the amount spent on
advertising, in thousands of dollars.
a) How many units were sold after spending \(\$ 1000\) on advertising?
b) Find \(N^{\prime}(a)\) and \(N^{\prime}(10)\)
c) Find the maximum and minimum values of \(N,\) if they exist.
d) Find \(N^{\prime}(a) .\) Discuss \(\lim _{q \rightarrow \infty} N^{\prime}(a)
.\) Does it make sense to spend more and more dollars on advertising? Why or
why not?