A car is traveling on a straight, level road under wintry conditions. Seeing a patch of ice ahead of her, the driver of the car slams on her brakes and skids on dry pavement for 50 m, decelerating at 7.5 m/s2. Then she hits the icy patch and skids another 80 m before coming to rest. If her initial speed was 70 mi/h, what was the deceleration on the ice?