Below Is a Representation of the Sparingly Soluble Salt MX

Below is a representation of the sparingly soluble salt MX at equilibrium in aqueous solution. (Each circle represents 1.0 ×10^-3 mol of atoms, and the volume of the box is 1.0 L. Solvent water molecules are omitted for clarity.) What is K_sp for MX?

A) 1.5 ×10^-5
B) 6.0 ×10^-6
C) 3.6 ×10^-1
D) 1.8 ×10^-3
E) 9.0 ×10^-6