Which ratios form a proportion? 3/15, 12/55 8/24, 12/35 5/18, 25/90 4/11, 16/25 what ratio forms a proportion with 9/15? 6/10 16/21 36/50 45/70

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?