The tortoise and the hare were in a 42 kilometer marathon. The rabbit
can run 5 times as fast as the tortoise. Less than halfway into the
race, the rabbit dropped his lucky rabbit's foot, and so stopped to try
and find it. After finding it, he started running to catch up with the
tortoise. When the tortoise reached the finishing line, the rabbit was 2
kilometers away. How far (in km) did the tortoise crawl while the
rabbit was looking for his lucky rabbit's foot?