Having problems with the worded questions like this

A population P(t) (where t is the time in years) undergoes yearly seasonal fluctuations such that the rate of population growth is proportional to a fraction rP(t) of the total population, where r = cos 2xt Initially, the population Is Po After 3 months (1e 3/12 years), the population grows to 110% of its initial size What is the maximum value that P(t) can attain? At what time(s) does P(t) attain its maximum