The population of a Midwestern city starts with 25,000 people in January 2010 and grows by 20% over each suc- cessive four-year period. (a) Find a formula for the population of the city, P, as a function of time, t, where t is the number of years after January 2010. (b) Find the annual and continuous growth rates of the city. (c) In what year does the population of the city reach 40,000?