Consider a max-heap of $n$ distinct integers, $n ≥ 4$, stored in an array $\mathcal{A}[1 . . . n]$. The second minimum of $\mathcal{A}$ is the integer that is less than all integers in $\mathcal{A}$ except the minimum of $\mathcal{A}$. Find all possible array indices of $\mathcal{A}$ in which the second minimum can occur. Justify your answer.