FlyUs Airlines is unhappy with the number of empty seats on its Sudbury to Toronto flight. To remedy the problem, the airline is offering a special discounted rate of $89 instead of the normal $169, but only for 7-day advance purchases and for a limited number of seats per flight. The aircraft flown from Sudbury to Toronto holds 100 passengers. Last month’s distribution of full-fare passengers is shown below. How many seats should FlyUs reserve for full-fare passengers?

Full-Fare                                        Frequency

50 ....................................................... 15

55 ....................................................... 20

60 ....................................................... 35

65 ....................................................... 20

70 ....................................................... 10