Suppose that, after measuring the duration of many telephone calls, a telephone company found their data was well-approximated by the density function $p(x) = 0.2 e^{-0.2 x}$, where $x$ is the duration of a call, in minutes.

(a) What percentage of calls last between 2 and 3 minutes?
Percent = percent

(b) What percentage of calls last 2 minutes or less?
Percent = percent

(c) What percentage of calls last 4 minutes or more?
Percent = percent

(d) What is the cumulative distribution function, $P(t)$?
$P(t) =$