Enthalpy of a $2$D super$-$alloy: Consider the AB super$-$alloy in $2$D as shown below. Assume the interactions are only between nearest neighbors, and the atomic interaction energies between $AA,B-B$ and $A-B$ are respectively $e_{AA},e_{BB}$ and $e_{AB}$ Derive the molar enthalpy of this alloy $($use $Na$ for Avogadro number$).$