(a) In decay of, say, a 226/88Ra nucleus, show that the nucleus carries away a fraction 1/...

Question:

(a) In α decay of, say, a 226/88Ra nucleus, show that the nucleus carries away a fraction 1/ (1 + 1/4AD) of the total energy available, where AD is the mass number of the daughter nucleus.
(b) Approximately what percentage of the energy available is thus carried off by the α particle in the case cited?