(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?

1001 0110 10-0 0011 1100 00- 0110 1101 0011 1010 0011 1010 1100 1100 0110 0011 1001 00-0 1110 1001