Arifle fires a 2.10 x 10-2 kg pellet straight upward, because the pellet rests on a compressed spring that is released when the trigger is pulled. the spring has a negligible mass and is compressed by 9.10 x 10-2 m from its unstrained length. the pellet rises to a maximum height of 6.10 m above its position on the compressed spring. ignoring air resistance and any other friction force, determine the spring constant.

be sure the answer is correct this means a lot to my grade this semester and i just can not seem to get it.