Lithium Fluoride Has a Lattice Energy of -1033 KJ/mol

Lithium fluoride has a lattice energy of -1033 kJ/mol. In the ionic solid AB, A²⁺ has approximately the same radius as Li⁺, and B^2- has approximately the same radius as F^?. What is a reasonable estimate of the lattice energy of AB?

A) About 3 × (-1033 kJ/mol)
B) About -1033 kJ/mol
C) About 4 × (-1033 kJ/mol)
D) About 2 × (-1033 kJ/mol)
E) About 6 × (-1033 kJ/mol)