4. Multi-Source Max-Flow. (10 points) Consider a variant of the max-flow problem where, instead of having just a single sources, the input graph G = (V. E) now has k sources S1, S2, ..., 8 Thus, the value of the flow is redefined to be the sum of the flows leaving all sources |SI = Di Evev f(si, v). Explain how you can transform graph G into another graph G' that has a single source and show how a max-flow solution to G' can be translated into a max-flow solution to the multi-source G. (Hint: recall that we did something similar for the bipartite matching problem). 3