There are two restaurants, A and B, in a small town. Customers arrive at the two restaurants according to a Poisson process with a mean rate of 2 and 3 per hour, respectively.

(a) Find the probabilities that there will be no more than 3 persons arriving at restaurant A in half an hour.

(b) Find the probability that in half an hour, the total number of customers arriving at restaurant A and restaurant B is no more than 1.