The Story of the Ship Captain

There is a ship about to sail. At the time of launch, the ship's engine suddenly died. The ship's captain immediately called for technicians to restart the engines, but their attempts were unsuccessful. The captain of the ship then asked who could fix this machine. Seen an old man raised his hand. This old man looks normal. Don't look like a machinist or an expert. But the captain of the ship had no choice. He asked the old man, " You can repair? "The old man nodded too. Then he and the captain of the ship went to the engine of the ship.
 

 Then the old man took an iron rod and knocked on the ship's engine. He said to the captain of the ship, "Now try to start". It turned out that the ship was alive. The ship's captain was surprised. The ship's captain asked how much the old man's service cost. The old man said, "US$ 3,000.00""What!" The captain of the ship was shocked again.

 "Why is it so expensive?" the captain asked. "Sir, tapping the machine is only US$ 100. But knowing where the exact location is to knock it is  US$2,900."The value of a person depends on expertise in the field. The more skilled a person is, the more he is needed