This lecture covers Quantum Electrodynamics (QED) calculations, focusing on Feynman diagrams, matrix element calculations, and interference terms. It explains how to calculate cross sections for decays and scattering processes, emphasizing the importance of lowest order diagrams. The lecture also delves into electron-positron annihilation, spin considerations, and chiral eigenstates in QED. It concludes with discussions on differential cross sections, resonant production, and the measurement of R(s) in various processes.