help with physics question?? - annihilation and pair production

4. Under certain circumstances, a photon moving through a material can interact with the nucleus of an atom of the material to produce an electron and a positron
c) Show that the minimum energy of the photon required for this process is 1.02 MeV
Which formula do I use? Is it just the same as if i were working out the minimum energy of a proton for example or is it something else?

https://filestore.aqa.org.uk/resources/physics/AQA-7408-SDB.PDF
I believe you work it out from the rest energies, which you can find here.
Photons have a rest energy of 0 MeV and both electrons and positrons have rest energies of around 0.51 MeV. Essentially it should be the sum of the rest energies of the products minus the sum of the rest energies of the original particles