The spring constant k = 1.5 x 10-2 Newtons/m and the Δs = 15.0 cm = 0.15 m.PE = \\[\\frac{1}{2}\\] ks2PE = \\[\\frac{1}{2}\\] x (1.5 x 10-2) Newtons/m (0.15 m)2PE = 1.69 x 10-4 Newtons/m = J