Brother Bernard is a very large dog with a taste for tobogganing. Ernie gives him a ride down Idiots' Hill---so named because it is a steep slope that levels out at the bottom for 10 m, and then drops into a river. When they reach the level ground at the bottom, their speed is 40 km/h, and Ernie, sitting in front, starts to dig in his heels to make the toboggan stop. He knows, however, that if he brakes too hard, he will be mashed by Brother Bernard. If the co efficient of static friction between the dog and the toboggan is 0.8, what is the minimum stopping distance that w ill keep Brother Bernard off Ernie's back?