Answer
$\begin{bmatrix}1&1&1\\-1&1&-1\\-1&1&-1\end{bmatrix}$
Work Step by Step
The matrix representing $T$ was determined in Exercise 29:
$A=\begin{bmatrix}2&2&2\\1&2&2\\1&2&1\end{bmatrix}$
If we desire to change the contrast we add 1 to each element corresponding to the dark grey color and add 1 to each element corresponding to the light grey color. The change matrix is:
$B=\begin{bmatrix}1&1&1\\-1&1&-1\\-1&1&-1\end{bmatrix}$
