please solve these two questions:

1)A spring with a spring constant of (5.63x10^4) N/m is stretched from an initial extension of (7.406x10^-2) m to a final extension of (3.689x10^-1) m. Calculate the work that must be done by the external force. Give your answer to 2 s.f.

2)Calculate the EPE of a collection of three particles (5.765x10^1) nC, (3.5180x10^1) nC and (1.000x10^1) nC, which are distances of r12 = (8.21x10^-1) m, r13 = (8.0270x10^-1) m and r23 = (4.977x10^-1) m respectively.