Solve the each part of given problem:
Problem: Hooke's law describes a certain light spring of unscratched length 36.0 cm. When one end is attached to the top of a door frame and a 6.40-kg object is hung from the other end, the length of the spring is 46.0 cm.
Part A: Find its spring constant?
Part B: The load and the spring are taken down. Two people pull in opposite directions on the ends of the spring, each with a force of 180 N. Find the length of the spring in this situation.
Please show all intermediate steps and formulas for above problem.