Suppose Bob has four cows that he wants to take across a bridge, but only
one yoke, which can hold up to two cows, side by side, tied to the yoke.
The yoke is too heavy for him to carry across the bridge, but he can tie
(and untie) cows to it in no time at all. Of his four cows, Mazie can cross
the bridge in 2 minutes, Daisy can cross it in 4 minutes, Crazy can cross
it in 10 minutes, and Lazy can cross it in 20 minutes. Of course, when
two cows are tied to the yoke, they must go at the speed of the slower cow.
Describe how Bob can get all his cows across the bridge in 34 minutes.