(1) Let the set $A=\left\{a_{1}, a_{2}, a_{3}, a_{4}\right\}$. If the set $B=\{-1,3,5,8\}$ consists of the sums of all three-element subsets of $A$, then the set $A=$ $\qquad$ .
(1) $\{-3,0,2,6\}$ Hint: Clearly, in all three-element subsets of $A$, each element appears 3 times, so
$$
3\left(a_{1}+a_{2}+a_{3}+a_{4}\right)=(-1)+3+5+8=15,
$$

Thus, $a_{1}+a_{2}+a_{3}+a_{4}=5$, so the four elements of set $A$ are $5-(-1)=$ $6,5-3=2,5-5=0,5-8=-3$, therefore, the set $A=\{-3,0,2,6\}$.