A husband and wife carry genes that make it possible for their children to have brown eyes (probability 0.60), blue eyes (0.30), or green eyes (0.10). Assume that the eye colors of the children are independent of each other.
a) What is the probability the first blue-eyed child they have is their fourth child? Give your answer to 2 decimal places.
b) On average, how many children would such a pair of parents have until having a blue-eyed child? Give your answers to 2 decimal places.