A manufacturer knows that their items have a normally distributed length, with a mean of 18.1 inches, and standard deviation of 3.7 inches. If one item is chosen at random, what is the probability that it is less than 28.9 inches long

One cell phone plan charges $20 per month plus $0.15 per minute used. a second cell phone plan charges $35 per month plus $0.10 per minute used. write and solve an equation to find the number of minutes you must talk to have the same cost for both calling plans.