1.
Let R1={(a,b)N×N:ab13}R_1 = \{(a, b) \in \mathbb{N} \times \mathbb{N}: |a - b| \le 13\} and R2={(a,b)N×N:ab13}R_2 = \{(a, b) \in \mathbb{N} \times \mathbb{N}: |a - b| \ge 13\}. Then on N\mathbb{N}: