What Is a Matrix Inverse?

$$A = \begin{bmatrix} 4 & 2 & -1 \\ 2 & 0 & 5 \\ -1 & 2 & 0 \end{bmatrix}$$

What is the sum of all the terms in $A^{-1}$?

Give your answer as a fraction in simplest form, with no spaces and a slash between the numerator and denominator (i.e. if your answer was $\frac{5}{57}$, you would submit "5/57").