Consider an ionic solid $MX$ with $NaCl$ structure. Construct a new structure $(Z)$ whose unit cell is constructed from the unit cell of $MX$ following the sequential instructions given below. Neglect the charge balance. $(i)\,\,\,\,\,$ Remove all the anions $(X)$ except the central one $(ii)\,\,\,\,$ Replace all the face centered cations $(M)$ by anions $(X)(iii)\,\,$ Remove all the corner cations $(M)(iv)\,\,\,\,$ Replace the central anion $(X)$ with cation $(M)$ The value of $$\,\,\left( {{{number\,\,of\,\,anions} \over {number\,\,of\,\,cations}}} \right)\,\,$$ in $Z$ is $\underline{\hspace{2cm}}$.