Manufacturing tennis balls According to the rules of tennis, a tennis ball is supposed to weigh between 56.7 grams (2 ounces) and 58.5 grams (2 1>16 ounces).

A machine for manufacturing tennis balls produces balls with a mean of 57.6 grams and a standard deviation of 0.3 grams when it is operating correctly. Suppose that the distribution of the weights is normal.

a. If the machine is operating properly, find the probability that a ball manufactured with this machine satisfies the rules.

b. After the machine has been used for a year, the process still has a mean of 57.6, but because of wear on certain parts, the standard deviation increases to 0.6 grams. Find the probability that a manufactured ball satisfies the rules.