4. A product is manufactured by four factories A, B, C and D. The unit production costs in them are ETB 2, ETB 3, ETB 1 and ETB 5 respectively. Their production capacities are 50, 70, 30 and 50 units respectively. These factories supply the product to four stories, demands of which are 25, 35, 105, and 20 units respectively. Unit transportation cost in ETB for each factory to each store is given in the table belo