Calculate the lattice energy for the hypothetical ionic compound M2X from the information given below.
IE1(M) = 473 kJ/mol
M(s) => M(g) ?Ho = 66.1 kJ/mol
?Hof(M2X) = -715.7 kJ/mol
X2(g) => 2X(g) ?H = 249 kJ
EA1+EA2 (X) = 1,021 kJ/mol
IE1 (X) = 271 kJ/mol