\text { 3. Consider the matrix } A \text { given below. } A=\left[\begin{array}{lll} 3 & 5 & 9 \\ 0 & 1 & 4 \\ 2 & 2 &

7 \end{array}\right] (a) Compute the determinant of A. (b) Compute the cofactor matrix cof(A) and use it to find the inverse of A.