A biologist estimates there are 600 animals of a certain species in a particular region. He expects the function P(t)=600(0.8)^t/20 to model the future population of the species, where P(t) is the population t years after the initial count. The range of the model function is a) P(t) is less than or equal to 600 b) 1< is less than or equal to P(t)is less than or equal to 600 c) 0 is less than or equal to P(t) is less than or equal to 600 d) P(t) is greater than or equal to 600