6. Draw the Feynman diagrams for the following processes. Remember that antiparticles propagate in the negative time direction. a. Electron-electron scattering via the exchange of a virtual photon. b. An atom absorbing a photon to go from the ground state to the excited state. c. Electron capture by a proton (weak force) to become a neutron. The diagram should be in terms of quarks and leptons. d. Positron emission by a proton (weak force) to become a neutron, also in terms of quarks and leptons. e. Electron-positron Annihilation to produce two photons.