Hooke's law describes a certain light spring of unstretched length 31.5 cm. When one end is attached to the top of a doorframe and a 7.17 kg object is hung from the other end, the length of the spring is 40.0 cm.
a) Find it's spring constant.
___kN/m
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 206 N. Find the length of the spring in this situation.
_____m