Find the numerical value of a in Eq. (41.8) for
(a) a hydrogen atom in which the nucleus is taken to be infinitely massive, so mt = m;
(b) Positronium (see Section 38.5), for which mt = m/2 exactly;
(c) Muonium, an atom composed of a muon and a proton (see Problem 38.59), for which mt = 185.8m. In part (a) a becomes a0 the Bohr radius.