Ayoung boy of mass m = 25 kg sits on a coiled spring that has been compressed to a length 0.4 m shorter than its uncompressed length and then held at this length. suddenly the spring is released, and the boy flies vertically into the air. he reaches a maximum distance 0.5 m above his initial position. the spring is ideal and massless and we ignore the air friction.

what is the spring constant k of the spring?

what is the speed of the boy when he is 0.4 meters above his starting position?