Solve the Problem $x$ Thousand Dollars on Advertising Is Given By $P(x)=1000+15 x-2 x^{2}$

Multiple Choice

Solve the problem.
-The profit from the expenditure of $x$ thousand dollars on advertising is given by $P(x) =1000+15 x-2 x^{2}$ . Find the marginal profit when the expenditure is $x=7$ .

A) 1000 thousand dollars/unit
B) -13 thousand dollars/unit
C) 105 thousand dollars/unit
D) 77 thousand dollars/unit