What is the strain energy stored in the specimen?

Question

A steel specimen 150mm² in cross – section stretches by 0.05 mm over a 50mm gauge length under an axial load of 30kN. What is the strain energy stored in the specimen? (Take E = 200GPa)                   

(a)0.75 N-m                         (b)1.00 N-m

(c)1.50 N-m                         (d)3.00 N-m