JEE Advanced 2018 Chemistry question

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 in **Z** is .