Suppose an Instructor or gave four 4 multiple choice questio

Suppose an Instructor or gave four [4] multiple choice questions on the and after giving the exam computed the probabilities of the number of problems correct for the students (which are given below)- what is the mean number of correct multiple-choice problems the instructor should expect to see?

The mean number of correct multiple choice problems the instructor should expect to use is

E(X)=0*0.08+1*0.18+2*0.26+3*0.35+4*0.13=2.27