I'm super stuck on this statistics question about probability. I only need help with option b. Thank you so much!

Assume that females have pulse rates that are normally distributed with a mean of u = 75.0 beats per minute and a standard deviation of o = 12.5 beats per minute. Complete parts (a) through (c) below. a. If 1 adult female is randomly selected, find the probability that her pulse rate is less than 82 beats per minute. The probability is 0.7123 . (Round to four decimal places as needed.) b. If 4 adult females are randomly selected, find the probability that they have pulse rates with a mean less than 82 beats per minute. The probability is (Round to four decimal places as needed.)