12. A cosmetic supply firm, which specialist in a door-to-door sales approach has found that the response of sales to the allocation of additional sales representatives behaves according to the law of diminishing returns. For one regional sales district, the company estimates that annual profit \( P \) , stated in \( R M \) , is a function of the number of sales representatives \( x \) assigned to the district. The profit function is given:
\( P = f ( x ) = - 12.5 x ^ { 2 } + 1375 x - 1500\)
a. What number of representatives will result in maximum profit for the district? b. What is expected profit?