POSSIBLE SOLUTION(S)

1. (Geometry Solution) Imagine that the campfire is on the opposite side of the river, which is infinitely thin. Then, it is clear that the shortest distance between the campfire and the car is a straight line path, and since this gets you to the river 400 feet from the fire, that must be the optimum place to aim for at the river bank.

1. (Calculus Solution)

2. To minimize the time, we use the fact that T = D / R.