Let $A=\left[a_{i j}\right]$ be a $3 \times 3$ matrix, where $a_{i j}=\left\{\begin{array}{cl}1, & i f i=j \\ -x, & i f|i-j|=1 \text {. Let a fucntion } f: R \rightarrow R \text { be defined as } f(x)= \\ 2 x+1, & \text { otherwise }\end{array}\right. \operatorname{det}(A)$. Then the sum of maximum and minimum values of $f$ on $R$ is equal to :