Use this sample space listing the eight simple events that are possible when a couple has three children (as in Example 2 on page 135): {bbb, bbg, bgb, bgg, gbb, gbg, ggb, ggg}. Assume that boys and girls are equally likely, so that the eight simple event  are equally likely. Find the probability that when a couple has three children, there is exactly one girl.

Use the given sample space or construct the required sample space to find the indicated probability.