9 The position vectors of points \(A\) and \(B\) relative to an origin \(O\) are given by
$$\overrightarrow { O A } = \left( \begin{array} { c }
p
1
1
\end{array} \right) \quad \text { and } \quad \overrightarrow { O B } = \left( \begin{array} { l }
4
2
p
\end{array} \right)$$
where \(p\) is a constant.
- In the case where \(O A B\) is a straight line, state the value of \(p\) and find the unit vector in the direction of \(\overrightarrow { O A }\).
- In the case where \(O A\) is perpendicular to \(A B\), find the possible values of \(p\).
- In the case where \(p = 3\), the point \(C\) is such that \(O A B C\) is a parallelogram. Find the position vector of \(C\).