You are the manager of sales development at MA Appliance. You have been hiring more external salespeople, hypothesizing that more salespeople mean more sales. The total cost of hiring is 5 + 3Q2, while the total benefit of hiring salespeople is 40Q-Q2, where Q is the number of salespeople.

a. What level of salespeople provides the highest maximum benefit?

b. What level of salespeople provides the least cost?

c. What is the optimal level of salespeople Why?