How about using this formula : -
For $n$ transactions $T_1$, $T_2$, $T_3$,...,$T_n$ having $n_1$, $n_2$, $n_3$, ... $n_n$ instructions each
\[ \frac {(n_1+n_2+n_3+...+n_n)!}{n_1 ! n_2 ! n_3! .... n_n!}-n!\]
So according to questing answer should be 68