In a remote mountain village, the only way to cross the river is by ferry. You need to give the boatman a dollar for a boat ride. Suppose you have no money, but there are three ways to replace it:
NO.1 Give a bunch of firewood to the boatman to replace the cost NO.2 Ferry for two hours yourself NO.3 Give your jacket to the boatman to replace the cost
Here are six permutations. According to the feasibility of the three methods, The most feasible one you think is in the front. Which one would you choose?