please suggest me the minimum overall dimension of the RCC slab to install following four washbasins of different shapes and sizes.

w d h (in cm)
1) 68x42x17.5
2) 65x48x14.5
3) 61x47x14.5
4) 60x38x12

Also suggest suitable position (wall mount or counter mount) of mixer for above wash basins.

Urgent response is requested