1. Let the set $A=\left\{a_{1}, a_{2}, a_{3}, a_{4}\right\}$ and all its three-element subsets' products form the set $B=\{24,30,40$, $60\}$, then $A=$ $\qquad$ .
Let $a_{1}<a_{2}<a_{3}<a_{4}$, then $\left\{\begin{array}{l}a_{1} a_{2} a_{3}=24, \\ a_{1} a_{2} a_{4}=30, \\ a_{1} a_{3} a_{4}=40, \\ a_{2} a_{3} a_{4}=60\end{array} \Rightarrow a_{1} a_{2} a_{3} a_{4}=3 \cdot 4 \cdot 10=120\right.$ $\Rightarrow\left(a_{1}, a_{2}, a_{3}, a_{4}\right)=(2,3,4,5)$. Therefore, $A=\{2,3,4,5\}$.