Answer
The energy that is released in this decay is $~~1.21~MeV$
Work Step by Step
We can find the amount of "missing" mass:
$\Delta m = 136.9071~u- 136.9058~u$
$\Delta m = 0.0013~u$
$\Delta m = (0.0013)~(1.66\times 10^{-27}~kg)$
$\Delta m = 2.158\times 10^{-30}~kg$
This mass is transformed into energy.
We can find the energy that is released in this decay:
$E = \Delta m~c^2$
$E = (2.158\times 10^{-30}~kg)(3.0\times 10^8~m/s)^2$
$E = 1.94\times 10^{-13}~J$
$E = (1.94\times 10^{-13}~J)(\frac{1~eV}{1.6\times 10^{-19}~J})$
$E = 1.21\times 10^6~eV$
$E = 1.21~MeV$
The energy that is released in this decay is $~~1.21~MeV$
