The number of minor surgeries, X, and the number of major surgeries, Y , for a policy-

holder, this decade, has joint cumulative distribution function

F(x, y) = [1 0.5^x+1][1 0.2^y+1], x > 0, y > 0.

Calculate the probability that the policyholder experiences exactly three minor surgeries

and at most three major surgeries this decade.