The atomic mass of $$_6C^{12}$$ is 12.000000 u and that of $$_6C^{13}$$ is 13.003354 u. The required energy to remove a neutron from $$_6C^{13}$$, if mass of neutron is 1.008665 u, will be :

Reaction equation: $$_{6}\text{C}^{13} \rightarrow {}_{6}\text{C}^{12} + {}_{0}\text{n}^{1}$$

Mass defect: $$\Delta m = \left[m\left({}_{6}\text{C}^{12}\right) + m_n\right] - m\left({}_{6}\text{C}^{13}\right)$$

$$\Delta m = [12.000000 + 1.008665] - 13.003354 = 13.008665 - 13.003354 = 0.005311\text{ u}$$

Energy required: $$E = \Delta m \times 931.5\text{ MeV} \implies E = 0.005311 \times 931.5 \approx 4.95\text{ MeV}$$