Answer:
U = 0.0207 J
Step-by-step explanation:
We know that:
U =

where U is the potential energy, K the constant of the spring and x is the deformation.
so, the deformation is calcualted as:
x = 0.146m-0.116m
x = 0.03m
Finally, replacing the values of x and K, we get:
U =

U = 0.0207 J