7. (16%) Compute the determinant of the following matrix C:

$$C = \begin{bmatrix} 1 & 12 & 0 & 0 \\ 0 & 14 & 0 & 0 \\ 0 & 16 & 1 & 0 \\ 0 & 18 & 0 & 1 \end{bmatrix}$$