Ron is planning for the back-to-school rush at his store. Last year he estimated that he would need 168 notebooks, but he sold 200 notebooks. Explain how Ron can find the percent error of his estimate.

The weekly amount spent by a company for travel has an approximately normal distribution with mean = $550 and standard deviation = $40. a) what is the probability that the actual weekly expense will exceed $570 for more than 20 weeks during the next year? (note: one year = 52 weeks) b) what is the probability that actual weekly expenses exceed $580 for 10 or more, but 16 or fewer weeks during the next year?