The following table shows the probability distribution for a discrete random
 variable.
 13
 16
 17
 21
 23
 25
 26
 31
 P(X) 0.07 0.21 0.17 0.25 0.05 0.04 0.13 0.08
 What is the mean of this discrete random variable? (That is, what is E(X), the
 expected value of X?)
 A. 21.5
 B. 22
 ) C. 21
 D. 20.42