The diameter of a brand of tennis balls is approximately normally distributed, with a mean of

2.59 inches and a standard deviation of 0.05 inch. A random sample of 10 tennis balls is selected. Complete parts (a) through (d) below.

b. What is the probability that the sample mean is less than 2.57 inches?

c. What is the probability that the sample mean is between 2.58 and 2.61 inches?

d. The probability is 68% that the sample mean will be between what two values symmetrically distributed around the population mean?

The lower bound is inches. The upper bound is inches.