Three units with the following specifications are listed: Unit 1: Coal fired: Maximum output = 1200 MW Minimum output = 350 MW Input-output curve: 1=510 7.21 0.0014212 (Mbtu/h) Unit 2: Oil fired: Maximum output = 1000 MW Minimum output = 300 MW Input-output curve: 2=310 7.852 0.0014222 (Mbtu/h) Unit 3: Oil fired: Maximum output = 800 MW Minimum output = 200 MW Input-output curve: 3=178 7.973 0.0048232 (Mbtu/h) Fuel costs for the three units are 1.2 R/Mbtu, 1.0 R/Mbtu and 1.0 R/Mbtu, respectively. Determine the economic operating point for these three units when delivering a total of 2000 MW