During 21 weeks at the height of an influenza outbreak, the rate at which the number of cases of infection changed could be approximated by I'(t)=-6.54t+ 142.2, where I is the total number of infected people and t is time measured in weeks. Answer parts a) through d). a) Estimate I(t), the total number of people who have contracted influenza by time t. Assume that I(0) = 1399.