3. A discrete random variable X has the following probability distribution: 77 78 79 80 81
P) 0.15 0.15 0.20 0.40 0.10

Compute each of the following quantities.
a. P(80)
b. P(X > 80).
c. P(X S80).
d. The mean p of X.
e. The variance a? of X.
f. The standard deviation o of X.