7. A family has two children. Let C be a characteristic that a child can have, and assume that each child has characteristic C with probability p, independently of each other and of gender. For example, C could be the characteristic "born in winter as in Example 2.2.7 Show that the probability that both children are girls given that at least one is a girl with characteristic C is -2 (which is 1/3 if p = 1, agreeing with the first part of Example 2.2.5, and approaches l/2 from below as p 0, agreeing with Example 22.7,)