In the following probability distribution (in table form), the discrete random variable X represents the number of activities the mother of a 6th-8th grade student is involved in.
x P(X = x)
0 0.10
1 0.137
2 0.27
3 0.302
4 0.191
a) Find the probability that a randomly selected mother is involved in at least two activities.
b) Find the probability that a randomly selected mother is involved in exactly three activities, given that she is involved in at least two activities.