6. (10%) Use Gauss elimination to find the inverse of the following matrix A. First, reduce the matrix to row echelon form, and then continue to reduced row echelon form to obtain the inverse matrix. $$A = \begin{bmatrix} 1 & 2 & 3 \\ 2 & 5 & 6 \\ 3 & 4 & 8 \end{bmatrix}$$