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.40% of shingled roofs in Oregon have a useful life between 27 years and how many years. 1/10 for values of x between 25 and 35
F(x) =
0 everywhere else

A) 32.5
B) 34
C) 33.2
D) 31
E) 30.6