Pion Radiation Therapy a neutral pion (0) has a mass of 264 times the electron mass and

Question:

Pion Radiation Therapy a neutral pion (π0) has a mass of 264 times the electron mass and decays with a lifetime of 8.4 x 10-17 s to two photons. Such pions are used in the radiation treatment of some cancers.
(a) Find the energy and wavelength of these photons. In which part of the electromagnetic spectrum do they lie? What is the RBE for these photons?
(b) If you want to deliver a dose of 200 rem (which is typical) in a single treatment to 25 g of tumor tissue, how many π0 mesons are needed?