Exercise.... Powerco has three electric power plants that supply the electric needs of four cities. The associated supply of each plant and demand of each city is given in the table as follows: The cost of sending 1 million kwh of electricity from a plant to a city depends on the distance the electricity must travel. From To City 1 City 2 City 3 City 4 Supply (Million kwh) Plant 1 58 56 $10 59 35 Plant 2 59 $12 $13 $7 50 Plant 3 $14 59 $16 $5 40 Demand 45 20 30 30 (Million kwh)