The number of supply points, the number of demand points, and the total supply in the balanced transportation problem

Question

A company has two factories S₁, S₂ warehouses D₁, D₂. The supplies from S₁ and S₂ are 50 and 40 units respectively. Ware house D₁ requires a minimum of 20 units and maximum of 40 units. Warehouse D₂ requires a minimum of 20 units and, over and above, it can take as much as can be supplied. A balanced transportation problem is to be formulated for the above situation. The number of supply points, the number of demand points, and the total supply (or total demand) in the balanced transportation problem respectively are             

      (a) 2, 4, 90                                                          (b) 2, 4, 110

      (c) 3, 4, 90                                                          (d) 3, 4, 110