4.4 Exercise 20

Two salesmen work differently. Roland spends more time with his customers than does Betty, hence tends to see fewer customers. On a given day Roland sees five customers and Betty sees six. The customers make decisions independently. If the probabilities for success on Roland's customers are $0 . 7 , 0 . 8 , 0 . 8 , 0 . 6 , 0 . 7$ and for Betty's customers are $0 . 6 , 0 . 5 , 0 . 4 , 0 . 6 , 0 . 6 , 0 . 4$, what is the probability Roland makes more sales than Betty? What is the probability that Roland will make three or more sales? What is the probability that Betty will make three or more sales?