Which of the following is the correct order of lattice energy

Question

$\begin{array}{1 1}(a)\;LiF < MgS < CaF_2&(b)\;LiF < CaF_2 < MgS\\(c)\;MgS < LiF < CaF_2 &(d)\;CaF_2 < LiF < MgS\end{array}$