Let

Let $A=\{2,3,4,5, \ldots, 17,18\}$. Let ' $\simeq$ ' be the equivalence relation on $A \times A$, cartesian product of $A$ with itself, defined by ( $a, b$ ) $\simeq$ $(c, d)$ if $a d=b c$. Then, the number of ordered pairs of the equivalence class of $(3,2)$ is

(a) 4
(b) 5
(c) 6
(d) 7