this question is from "Design and Analysis Algorithm" class. I am not understanding the question. please solve it correctly and explain.

Solve equation X()X=X for all 22 real-valued matrices, where () - modified multiplication where + changed to min and x changed to + (from slides). (HINT 2-vertex graphs w/o neg cycle) ab cd Hint: the top-left position of ab.ab x cdcd equals min{2a,b+c}