$($b$)$ Four Companies A$,$ B$,$ C$,$ D supply requirement of three warehouses $x,Y,Z$ respectively. The companies availability, warehouse requirements and the unit cost of transportation are given in the following table. Find the initial basic feasible solution using :

$($i$)$ Least cost method.

$($ii$)$ Vogel approximation method.

$($iii$)$ North West Corner method.