Using Vogel's Approximation method, solve the following transportation problem : Factory Distributors D1 D2 D3 D4 Availability 01 21 16 25 13 11 02 17 18 14 23 13 03 32 27 18 41 19 Requirement 6 10 12 15 Also solve the above Transportation Problem by North West Corner Method and obtain the optimum solutions.