I'm stuck on part b

x 8.3.4/-BE Suppose that profits on the sale of swimming suits in a department store are given approximately by the function below where P(t) is profit (in hundreds of dollars) for a week of sales t weeks after January 1. Answer a) through e) below. P(t) = 5 -5 cos (# ).051536 a) What is the rate of change of profit t weeks after the first of the year? P' (t) = 9 sin 9 (Type an exact answer, using it as needed.) b) What is the rate of change of profit 5 weeks after the first of the year? 9 weeks after the first of the year? 16 weeks after the first of the year? ncorr P'(5) = (Round to two decimal places as needed.)