During 20 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) = - 6.46t+ 142.4, 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) = 1428. I(t) = b) Approximately how many people contracted influenza during the first 8 weeks? people (Round to the nearest integer as needed.) c) Approximately how many people contracted influenza during the whole 20 weeks? people (Round to the nearest integer as needed.) d) Approximately how many people contracted influenza during the last 7 of the 20 weeks? people