11. The determinant $\left| \begin{array}{ll} a & b \\ c & d \end{array} \right|$ where $a, b, c, d \in \{-1, 1, 2\}$. Among all possible values, the maximum is $\_\_\_\_$
11. The determinant $\left| \begin{array}{ll} a & b \\ c & d \end{array} \right|$ where $a, b, c, d \in \{-1, 1, 2\}$. Among all possible values, the maximum is $\_\_\_\_$\\