The lattice can either be ZnS or NaCl type.......as both exhibit fcc lattice
in NaCl the edge length = 2(r+) + 2 (r-) [r+ is radius of the cation & r- is radius of anion ]
since in NaCl type Na is present on each edge and centre , Chlorine on each corner and face center
so we get r(-)=144 pm
in ZnS type then we get a diiferent answer not in the options by using root(3)a = 4[r(+) + r (-)]