In a seasonal-growth model, a periodic function of time is introduced to account for seasonal variations in the rate of growth. Such variations could, for example, be caused by seasonal changes in the availability of food. (a) Find the solution of the seasonal-growth model where k, r, and ϕ are positive constants. dP dt = kP cos(rt − ϕ) P(0) = P0 P(t) = (b) Find lim t→[infinity] P(t). (If there is no solution, enter NONE in the answer box.) lim t→[infinity] P(t) =