The spring is unstretched when x = 0. If the body moves from the initial position x1 = 1...

The spring is unstretched when x = 0. If the body moves from the initial position x₁ = 100 mm to the final position x₂ = 200 mm, (a) determine the work done by the spring on the body and (b) determine the work done on the body by its weight.