A city planner developed the function P to model the population of a city over the next 25 years, where P(t) is the projected population of the city t years from now. According to the model, which of the following gives the rate at which the population of the city will be changing at time t=5 ?
A) P(5)
B) P(6)−P(4)
C) P(5)/5
D) P'5