Pushing on the pump of a soap dispenser compresses a small spring. When the spring is compressed

Question:

Pushing on the pump of a soap dispenser compresses a small spring. When the spring is compressed 0.50 cm, its potential energy is 0.0025 J.
(a) What is the force constant of the spring?
(b) What compression is required for the spring potential energy to equal 0.0084 J?