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 is the standard deviation of the useful life distribution? 1/10 for values of x between 25 and 35
F(x) =
0 everywhere else

A) 2.886
B) 3.446
C) 2.467
D) 4.890
E) 5.118