3 You are given that \(\mathbf { A } = \left( \begin{array} { c c c } \lambda & 6 & - 4
2 & 5 & - 1
- 1 & 4 & 3 \end{array} \right) , \mathbf { B } = \left( \begin{array} { c c c } - 19 & 34 & - 14
5 & - 5 & 5
- 13 & 18 & - 3 \end{array} \right)\) and \(\mathbf { A B } = \mu \mathbf { I }\), where \(\mathbf { I }\) is the \(3 \times 3\) identity
matrix.

1. Find the values of \(\lambda\) and \(\mu\).
2. Hence find \(\mathbf { B } ^ { - 1 }\).