Solution Strategy (cont.)
Suppose the load power increases by a small increment DP.
How should DP be split between the two units?
The answer is: because its cheaper than # 2 (i.e., l1 < l2), use # 1 to serve all of DP.
l1(25) = 2.50 $/MWh & l2(30) = 2.84 $/MWh.