A rope is thrown from the road from point C out into the snow and lands at point A. A dog runs from point C along the road to point B and then jumps into the snow and runs directly from B to A to retrieve the rope. The dog wants to enter the snow at a point that minimizes its total time (time on the road plus time in the snow) to retrieve the rope. You can move the point B to map out the total time (in red) that the dog needs to reach the rope and see when it is the smallest value. You can change the running speed in land and snow of the dog using the green and blue sliders. You can also move point A, where the rope lands in the snow.