15) 3.4.7(192) Recall that the Poisson distribution with a parameter value of y=np can be used to approximate the B(n, p) distribution when n is very large and the success probability p is very small. A box contains 500 electrical switches, each one of which has a probability of 0.005 of being defective. Use the Poisson distribution to make an approximate calculation of the probability that the box contains no more than three defective switches.