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.

(a) Write a formula for W, the GWP (in trillions of dollars), as a function of years, t, since 2004.
$W(t) =$ help (formulas)

(b) Estimate the value of t when the GWP is predicted to reach 70 trillion dollars.
$t =$ (Round to the nearest 0.1 years.) help (numbers)