exponential function problem

one weird problem:

Throughout much of the 20th century, the yearly consumption of electricity in the US increased exponentially at a continuous rate of 4% per year. Assume this trend continued and that the electrical energy consumed in 1900 was 2 million megawatt-hours.

(a) Write a formula for yearly energy consumption, C, in millions of megawatt-hours as a function of time, t, in years since 1900.

(b) Find the average yearly electrical consumption throughout the 20th century.

(c) During what year was electrical consumption the closest to the average for the century?

for the part (a) I tried "C=2*(1.04)^(t-1900)" but it says wrong. So I couldn't go further...

thanks,

Tuugii