Chapter 4.2, Problem 90E

Revenue. A national food service runs food concessions for sporting events throughout the country. The company’s marketing research department chose a particular football stadium to test market a new jumbo hot dog. It was found that the demand for the new hot dog is given approximately by

     $\begin{array}{cccc}p& =& 8-2\ln x& 5\le x\le 50\end{array}$

where x is the number of hot dogs (in thousands) that can be sold during one game at a price of $p.

1. (A) Find the local extrema for the revenue function.
2. (B) On which intervals is the graph of the revenue function concave upward? Concave downward?