A spring with a spring constant of 3200 N/m is initially stretched until the elastic potential energy

Question:

A spring with a spring constant of 3200 N/m is initially stretched until the elastic potential energy of the spring is 1.44 J. (U = 0 for the relaxed spring.) What is ∆U if the initial stretch is changed to
(a) A stretch of 2.0 cm,
(b) A compression of 2.0 cm, and
(c) A compression of 4.0 cm?