A 1.5-kg box that is sliding on a frictionless surface with a speed of approaches a horizontal

Question:

A 1.5-kg box that is sliding on a frictionless surface with a speed of approaches a horizontal spring. (See Fig. 5.19.) The spring has a spring constant of 2000 N/m. If one end of the spring is fixed and the other end changes its position,
(a) How far will the spring be compressed in stopping the box?
(b) How far will the spring be compressed when the box’s speed is reduced to half of its initial speed?