A radium nucleus (mass 226 u) at rest decays into a radon nucleus (symbol Rn, mass 222

Question:

A radium nucleus (mass 226 u) at rest decays into a radon nucleus (symbol Rn, mass 222 u) and an alpha particle (symbol a, mass 4 u).
(a) Find the ratio of the speeds va / vRn after the decay.
(b) Find the ratio of the magnitudes of the momenta p a / pR.
(c) Find the ratio of the kinetic energies Ka / KRn. ("u" is a unit of mass; it is not necessary to convert it to kg.)