In the Compton Effect, a 0.100-nm photon strikes a free electron in a head-on-collision and knocks it

Question:

In the Compton Effect, a 0.100-nm photon strikes a free electron in a head-on-collision and knocks it into the forward direction. The rebounding photon recoils directly backward. Use conservation of (relativistic) energy and momentum to determine
(a) The kinetic energy of the electron, and
(b) The wavelength of the recoiling photon.