I am facing this problem, it may appear that I am asking an answer for homework, but it is not.
The solution is quite easy, however the new output of one of the units is greater than the max output, in this case, unit 3 new output is 157MW. I asked to my professor how should I approach the question if this issue appears, He said it should be obvious and I should think about it.
Then...I am thinking and thinking and thinkig, and I can not see a solution different from taking the excess from unit 3 and give it to unit 4 for example, however, i am sure it is not easy like that and it must have a mathematical explanation and more important, an important concept i am missing.
Could you help me understand what I am missing here? thanks