Given four parallel generating unit U. & U2 (oil fired) are identical, U3 (gas fired) & U4 (coal fired) where their input-output fuel cost functions are as follow: UI: F1 ($/h) = 300 +3*(P1) +0.03*(P.)2 U2: F2(S/h) = 200 + 1*(P2) +0.01"(P2) U3: F3 ($/h) = 400 + 4*(P) +0.04*(P:)? U4: F4 ($/h) = 200+ 2*(P4) +0.02*(P4) 20MW