In 2011 a country's federal receipts (money taken in) totaled $2.43 trillion. In 2013, total federal receipts were $2.75 trillion. Assume that the growth of federal receipts, F. can be modeled by an exponential function and use 2011 as the base year (t = 0). a) Find the growth rate k to six decimal places, and write the exponential function F(t), for total receipts in trillions of dollars. b) Estimate total federal receipts in 2015. c) When will total federal receipts be $12 trillion? a) Find the growth rate k. (Do not round until the final answer. Then round to six decimal places as needed.)