Let X denote the number of living grandparents that a randomly selected adult American has. According to recent General Social Surveys, its probability distribution is approximately P(0) = 0.71, P(1)= 0.15, P(2) = 0.09, P(3) = 0.03, P(4) = 0.02.

A)Does this refer to a discrete or a continuous random

variable? yes or no? Why?

B)Find the mean of this probability distribution.