An oil company discovered an oil reserve of $200$ million barrels. For time $t>0,$ in years, the company's extraction plan is a linear declining function of time as follows:

$q(t)=a-bt,$

where $q(t)$ is the rate of extraction of oil in millions of barrels per year at time $t$ and $b=0\mathrm{.}2$ and $a=30.$

How long does it take to exhaust the entire reserve?

Round your answer to one decimal place.

$t=$

$3$

years