Matrix A has size [math]3×2[/math], and matrix B has size .[math]2×3[/math]. It is known that AB = [math]\begin{matrix} 8 & 2& -2\\ 2 & 5& 4\\ -2 & 4& 5 \end{matrix}[/math] and the matrix BA is nondegenerate. If C=BA, then the sum of all elements of the matrix C equals _________