In 2011 a country's federal receipts (money taken in) totaled $2.10 trillion. in 2013, total federal receipts were $2.83 trillion. assume that the growth of federal receipts, f, can be modeled by an exponential function and use 2011 as the base year (tequals0). 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 $10 trillion?