How many unit cells are present in a cube shaped ideal crystal of NaCI of mass 1.00 g?[Atomic masses Na = 23, C1= 35.5]

NaCl has F.C.C structure .One unit cell of NaCl has 4 formula units.Mass of one unit cell of NaCl is58.5×4 a.m.u∴ Mass of one mole of unit cells of NaCl is 58.5×4gm   4×58.5 gm of NaCl --   6.023×1023 unit cells of NaCl    1gm of NaCl                                  ?  6.023×1023×14× 58.5 gm =  2.57×1021 unit crlls