A culture of yeast grows at a rate proportional to its size. If the initial population is 8000 cells and it doubles after 4 hours, answer the following questions. 1. Write an expression for the number of yeast cells. after t hours. Answer: P(t) = 2. Find the number of yeast cells after 5 hours. Answer: 3. Find the rate at which the population of yeast cells is increasing at 5 hours. Answer (in cells per hour):