18. The prot P (in dollar) from selling 1; laptop computer is given by (5 points) P = 0_04x2 + 25x1500 a. Find the marginal prot when x :150 b. Explain the result 19. Irene has just started a new job. At the beginning of each quarter she deposits $250 into 401-k plan which earns 4.4% annual interest compounded continuously. How much will she have in her account after 15 years? (10 points)