请认真阅读下面短文，并根据短文内容回答问题。
Jeff Keith has only one leg. When he was 12 years old, Jeff had cancer. The doctors had to cut off most of his right leg to save his life. Every day Jeff puts on a man-made leg. The leg is plastic. With the plastic leg, Jeff can ski, ride a bicycle, swim and play soccer. He can also run.
When he was 22 years old, Jeff ran across the United States, from the East to the West. He ran 5,150 kilometers. That's about 26 kilometers each day. Jeff wore out 36 pairs of running shoes and five plastic legs.
On his way, in every city people gave Jeff money. The money which Jeff received was not for Jeff himself. It was for the American Cancer Society(协会). The society used the money to learn more about cancer. At the same time, Jeff talked to people about cancer. He also talked about being disabled.
Jeff is disabled, but he can do many things: skiing, swimming, playing soccer and running. He finished college and now he is studying to be a lawyer(律师). Jeff says, “People can do anything they want to do. I want people to know that. I ran not only for disabled people but also for everybody.”
（1）、Why did the doctors cut off most of Jeff's right leg?
（2）、How many plastic legs did Jeff wear out when he ran across the United States?
（3）、What did Jeff talk to people about on his way from the East to the West?
（4）、Did he only run for the disabled people?
（5）、What can we learn from this story?
