The 2006 population of a particular region was 4.0 million and growing at an annual rate of 3.5%.
(a) Find an exponential function for the population of this region at any time t. (Let P represent the population in millions and let t represent the number of years since 2006.)
(b) What will the population (in millions) be in 2024? (Round your answer to two decimal places.)
(c) Estimate the doubling time in years for this region's population. (Round your answer to two decimal places.)