(18): $A = \{ 1,2,3,4,\ldots\ldots,10\};B = \{ 0,1,2,3,4\}$\\ $R = \left\{ (a,b) \subset A \times A:2(a - b)^{2} + 3(a - b) \in B \right\}$ Now, $2(a - b)^{2} + 3(a - b) = (a - b)|2(a - b) + 3| \in B$\\ $\Rightarrow a = b$ or $a - b = - 2$\\ When, $a = b \Rightarrow 10$ ordered pairs\\ When, $a - b = - 2 \Rightarrow 8$ ordered pairs. Total $= 18$