The graph in the figure below shows the magnitude of the force exerted by a given spring as a function of the distance x the spring is stretched. How much work is needed to stretch this spring: (a) a distance of 5.0 cm, starting with it unstretched, and (b) from x = 2.0 cm to x = 7.0 cm?
F (N)
350
300
250
200
150
100
50
1
Lx (cm)
1 2 3 4 5 6 7 8