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 52 , decelerating at 8.5 . Then she hits the icy patch and skids another 84 before coming to rest. If her initial speed was 76 , what was the magnitude of the deceleration on the ice?