(a) Explain why two digraphs are equivalent under relabeling of vertices and edges if and only if their incidence matrices satisfy PAQ = B. where P. Q are permutation matrices.
(b) Decide which of the following incidence matrices produce the equivalent digraphs:
(i)

(ii)

(iii)

(iv)

(v)

(vi)

(c) How are the cokernels of equivalent incidence matrices related?

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