For Exercises 1116, assume that C(x) and R(x) are in dollars and x is the number of units produced and sold. 13. For the total-revenue function R (x ) = 2x, find AR and R'(x) when x = 70 and Ax = 1.15. a) Using C(x) from Exercise 11 and R(x) from Exercise 13, find the total profit, P(x). b) Find AP and P' (x) when x = 70 and Ax = 1