In order to concentrate galena (which contains ZnS as impurity) by froth-floatation process, sodium cyanide is used as depressant. NaCN dissolves ZnS due to formation of water soluble complex (A).

Find $\frac{w+x}{y+z}$

Where w = coordination number of central metal ion in complex ion of (A)

x = number of unpaired electrons in (A)

 y = total number of possible linkage isomers of (A) including (A)

z = maximum number of atoms in a single plane in the complex ion of (A)