An insurance company offers its policyholder a number of different premium payment options. For a randomly selected policyholder, let X = the number of months between successive payments. The cdf of X is as follows: X 1 3 4 6 12 F(X) 0.30 0.40 0.45 0.60 1.00 a.) What is the pmf of X? b.) What is P ( 3