$\begin{aligned}
\Delta m & =\left(m_p+m_e\right)-m_n \
& =9 \times 10^{-31} \mathrm{kg}.
\end{aligned}Energyreleased=\left(9 \times 10^{-31} \mathrm{kg}\right) \mathrm{c}^2joules\begin{aligned}
& =\frac{9 \times 10^{-31} \times\left(3 \times 10^8\right)^2}{1.6 \times 10^{-13}} \mathrm{MeV} \
& =0.73 \mathrm{~MeV} .
\end{aligned}$