Cash Social Security distributions were $35 million, or $0.035 billion, in 1940. This amount has increased exponentially

Question:

Cash Social Security distributions were $35 million, or $0.035 billion, in 1940. This amount has increased exponentially to $683 billion in 2009. (Source: Social Security Administration) Assuming the exponential growth model applies:
a) Find the exponential growth rate k.
b) Find the exponential growth function.
c) Estimate the total cash distributions in 1965, in 1995, and in 2015.
d) In what year will the cash benefits reach $2 trillion?