Ellen is taking 4 courses for the semester.She believes that the probability distribution function for the number of courses in which she will get an A grade is given below.

X 0 1 2 3 4 P(X) 0.10 0.50 0.20 0.15 0.05

a) (2 pts) What is the random variable in this problem? Describe it.

b) (3 pts) What is the probability that Ellen will get at least 2 A's?

c) (3 pts) Find the mean and standard deviation the probability distribution.