In 2004 the gross world product, W, (total output in goods and services) was 54.7 trillion dollars and growing at a continuous rate of 3.8% per year.

Required:
a. Write a formula for W, the GWP (in trillions of dollars), as a function of years, t, since 2004.
b. Estimate the value of t when the GWP is predicted to reach 85 trillion dollars