Glenn needs 1,500 boards to build a small rocket. Each board must be 3 feet long. If boards are sold in 12 foot lengths, how many boards must Glenn buy and cut into 3 foot pieces to get the 1,500 he needs?

**NOTE : Please ignore the kerf (the width of the cut a saw makes, often about an eighth of an inch)

① 42

② 125

③ 375