Determine whether AC is defined. If it is defined, express the result as a single matrix; if it is not, say "not defined." \[ A=\left[\begin{array}{rrr} 0 & 1 & -6 \\ 1 & 1 & 6 \end{array}\right], B=\left[\begin{array}{rrr} 6 & 1 & 0 \\ -1 & 4 & -4 \end{array}\right], C=\left[\begin{array}{rr} 1 & 1 \\ 4 & 3 \\ -2 & 5 \end{array}\right] \]

Step 1 ：We are given matrices A and C. Matrix A is a 2x3 matrix and matrix C is a 3x2 matrix.

Step 2 ：The product of two matrices is defined if the number of columns in the first matrix is equal to the number of rows in the second matrix.

Step 3 ：In this case, matrix A has 3 columns and matrix C has 3 rows, so the product AC is defined.

Step 4 ：We can find the product by multiplying each element in the rows of the first matrix by the corresponding element in the columns of the second matrix and then summing these products.

Step 5 ：Performing these operations, we find that the product of matrices A and C is \[AC=\left[\begin{array}{rr} 16 & -27 \\ -7 & 34 \end{array}\right]\]

Step 6 ：\(\boxed{AC=\left[\begin{array}{rr} 16 & -27 \\ -7 & 34 \end{array}\right]}\) is the final answer.