A sled is moving down a steep hill in a straight line. At time t s, the acceleration of the sled is a m s−2 where

( )
1 2 3 20
500
a t t = − , 0 ⩽ t ⩽ 20. When t = 0 the sled is at rest at the top of the hill. Find the distance the sled
travels in the first 10 s of its motion.