Let R be a relation on N x N defined by (a, b) R (c, d) a + d = b + c for all (a, b), (c, d) N x N.
Show that:
i. (a, b) R (a, b) for all (a, b) N x N
ii. (a, b) R (c, d) (c, d) R (a, b) for all (a, b), (c, d) N x N
iii. (a, b) R (c, d) and (c, d) R (e, f) (a, b) R (e, f) for all (a, b), (c, d), (e, f) N × N