Federal Helium Reserve held roughly 16 billion cubic feet of helium in 2010, and is being reduced by about 2.1 billion cubic feet each year.
a. Provide the linear equation for remaining federal helium reserves, R, in terms of t, number of years since 2010.
b. In 2015, find helium reserves?
c. If rate of depletion does not change, when will Federal Helium Reserve be reduced??