2 Points \(A , B\) and \(C\) have position vectors \(- 5 \mathbf { i } - 10 \mathbf { j } + 12 \mathbf { k } , \mathbf { i } + 2 \mathbf { j } - 3 \mathbf { k }\) and \(3 \mathbf { i } + 6 \mathbf { j } + p \mathbf { k }\) respectively, where \(p\) is a constant.
- Given that angle \(A B C = 90 ^ { \circ }\), find the value of \(p\).
- Given instead that \(A B C\) is a straight line, find the value of \(p\).