An insurance company offers its policyholders 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: F(x)=0,x<10.30,1≤x<30.40,3≤x& lt;40.45,4≤x<60.60,6≤x<121,∗∗ ∗∗12≤x
a. What is the pmf of X?
b. Using just the cdf, compute
P(3≤X≤6)and P(4X)