I cant figure out how to set up the integrals.

Question

1.If the work required to stretch a spring 3 ft beyond its natural length is 15 ft-lb, how much work is needed to stretch it 27 in. beyond its natural length?

2.A spring has a natural length of 12 cm. If a 28-N force is required to keep it stretched to a length of 20 cm, how much work W is required to stretch it from 12 cm to 16 cm? (Round your answer to two decimal places.)

Answer 1

F = kx --- use that to get k.
work = ∫F(x) dx