(a) Briefly explain you are going to handle the following transportation problems   (i) Prohibited transportation problems (ii) Unbalanced transportation Problem   (b) Wasantha Trading Company (WTC) owns three factories, F1, F2, F3, producing 1000, 700, 300 tons of goods respectively These goods used to be four distribution centers, D1, D2, D3 and D4, needing 500 tons each. The costs of transportation per ton (in Rs. 000 )between the various factories and distribution centers are as follows;   To/ From D1 D2 D3 D4   F1 12 6 11 16 F2 8 15 14 5 F3 10 9 7 13   (i) Construct an initial feasible solution using Vogel's Approximation Method (VAM) to minimize total transportation cost. (ii) Find the optimal solution using the "MODI" method to minimize the total transportation cost.