The Useful Life (In Years) of a Shingled Roof in Oregon

Multiple Choice

The useful life (in years) of a shingled roof in Oregon has a uniform distribution described by the probability density function below.What proportion of roofs have a useful life of between 28.5 years and 29.5 years? 1/10 for values of x between 25 and 35
F(x) =
0 everywhere else

A) .15
B) .10
C) .30
D) .25
E) .20