In the Born-Haber cycle for the formation of an ionic compound , the following enthalpy values (in ) — Chemical Bonding Chemistry Question

Question

In the Born-Haber cycle for the formation of an ionic compound $MX(s)$, the following enthalpy values (in $kJ/mol$) are given: $\Delta H_f = -400$, $\Delta H_{sub} (M) = 100$, $IE (M) = 500$, Bond dissociation enthalpy of $X_2 = 200$, Lattice enthalpy of $MX(s) = -800$. What is the magnitude of the electron gain enthalpy (in $kJ/mol$) for the formation of $X^-(g)$?