An area of interconnected power system has two fossil-fuel units operating on economic dispatch. The variable operating costs of these units are given by: C₁ =10P+8 x 10³P S/hr C₂ = 8P2+9x 10-³P2 $/hr where P1 and P2 are in megawatts. If the load demand varies from 500 to 1500 MW, to help the operator minimizing the total cost. Determine: a) The power output from each unit. b) The incremental operating cost.