For the `beta^(+)` (positron) emission from a nucleus, there is another competing process known as electron capture (electron from an inner orbit, say, the K–shell, is captured by the nucleus and a neutrino isemitted).
`e^(+)+""_(Z-1)^(A)Y+V`
Show that if `beta^(+)` emission is energetically allowed, electron capture is necessarily allowed but not vice–versa.