Let the random variable X be the number of days that a patient stays in hospital after a surgical procedure. Assume that X = 1, 2, 3 or 4, and that the probability mass function for X is

1x f(x)=P(X=x)= , x=1,2,3,4

Find the expected number of days that a patient will have to stay in hospital.

A) 2.5 B) 4

C) 1 D) 2 E) 3