In a Ballistics Test, a Bullet Moving Horizontally with a Speed

Short Answer

In a ballistics test, a bullet moving horizontally with a speed of 500 m/s strikes a sandbag
and penetrates a distance of 10.0 cm.
(a) What is the magnitude of the average acceleration of the bullet in the sandbag?
(b) How many milliseconds does it take the bullet to come to rest in the sandbag?