(1) Explain why a graph contains no cycles if and only if DFS yields no back
    edges.  Use the definition of back edges given in the project description.
    You need not give a formal proof, just a good, intuitive argument in
    words.

(2) The algorithm given in the project description for finding strongly 
    connected components seems to have nothing to do with SCCs.  Provide 
    some intuitive justification for why it works.  Again, a formal proof
    is not required.  A cogent argument is.