In 2011 a​ country's federal receipts​ (money taken​ in) totaled​$2.36trillion. In​ 2013, total federal receipts were ​$2.68 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?