9.9. One-fourth of the married couples in a distant society have no children at all. The other three-fourths of families continue to have children until the first girl and then cease childbearing. Assume that each child is equally likely to be a boy or girl.

(a) For k = 0, 1, 2, . . . , what is the probability that a particular husband will have k male offspring?

(b) What is the probability that the husband's male line of descent will cease to exist by the 5th generation?