With a halogen X, a metal M forms ionic compounds MX, MX2 and MX3. The lattice energies of the compounds are -1340, -3840 and -7020 kJ/mol, respectively.

Question

With a halogen X, a metal M forms ionic compounds MX, MX2 and MX3. The lattice energies of the compounds are -1340,  -3840 and -7020 kJ/mol, respectively. 
The ionization energies of the metal are 360 (for M+), 1236 (M2+) and 2990 (M3+) kJ/mol and the sublimation energy is 334 kJ/mol. Will MX and/or MX2 disproportionate?

I have no idea where to start, so any advice is highly appreciated.