In 2007 us consumption of renewable energy was 68

Question

Renewable energy:-

In 2007, U.S. consumption of renewable energy was 6.8 quadrillion Btu (or 6.8 X 10¹⁵Btu). Since the 1960s, consumption has been growing at a rate (in quadrillion Btu s per year) given by

f'(t)=0.004t + 0.062

where t is years after 1960. Find f(t) and estimate U.S. consumption of renewable energy in 2020.