Tom lives one block from a high school football stadium（体育场）.One day，he decided he needed some money.His mother suggested that,with many people walking past their house almost every Saturday,he might try to sell something.That's when he came up with his great idea-selling apples.
The next Thursday afternoon Tom rode his bike to a farm stand（摊点）.The farmer was selling just-picked apples.Tom chose the best apples he could find. He then put theapples into the basket of his bike and headed for home.
On Friday Tom invited his little sister and her friends to work with him. He asked them to wash and shine the apples.He put the big ones into one pile and the smaller ones into another.
Saturday was the day of a big football game.That morning Tom set up his apple stand.He hung a sign on it saying,'Apples.Large 10 cents.Small 5 cents.'Around noon people started walking past the stand.He started selling apples.Long before the game began,he had sold every single apple.
Tom then sat down to see what he had earned.He counted five dollars and twenty cents.He subtracted（减除）one dollar and a half that he had paid for the apples.He subtracted another dollar that he had paid his little sister and her friends.He was two dollars and seventy cents richer.He began thinking of making his business larger.
How much money did Tom earn for himself?