A pion at rest decays into a muon and a neutrino: μ+v. The pion has a mass m = 140 MeV/c², the muon has a mass m₁ = 106 MeV/c2, and the neutrino is massless. Find the kinetic energy of the muon. Show all work. (Hint: Try to write down the final energy in terms of just the muon energy and muon mass.)