A block is acted on by a force that varies as (2.0 104 N/m) x for

Question:

A block is acted on by a force that varies as (2.0 × 104 N/m) x for 0 ≤ x ≤ 0.21 m, and then remains constant at 4200 N for larger x. How much work does the force do on the block in moving it
(a) From x = 0 to x = 0.30 m,
(b) From x = 0.10 m to x = 0.40 m?