A free neutron undergoes beta-decay to a proton, having a half-life...

The beta-decay of a free neutron is represented by the equation:

$n \rightarrow p + e^{-} + \bar{\nu}_{e}$

The energy liberated ($Q$-value) during this process is given by the mass defect:

$Q = (m_{n} - m_{p} - m_{e})c^{2}$

Using the standard rest mass energies:
Rest mass energy of neutron, $m_{n}c^{2} = 939.565 \text{ MeV}$
Rest mass energy of proton, $m_{p}c^{2} = 938.272 \text{ MeV}$
Rest mass energy of electron, $m_{e}c^{2} = 0.511 \text{ MeV}$

Substituting these values:

$Q = 939.565 - 938.272 - 0.511$

$Q = 0.782 \text{ MeV}$

$Q = 782 \text{ keV}$

The half-life of $14 \text{ minutes}$ is extra information not required for this calculation.