9 With respect to the origin \(O\), the points \(A , B\) and \(C\) have position vectors given by $$\overrightarrow { O A } = \left( \begin{array} { r } 2
1
- 3 \end{array} \right) , \quad \overrightarrow { O B } = \left( \begin{array} { l } 0
4
1 \end{array} \right) \quad \text { and } \quad \overrightarrow { O C } = \left( \begin{array} { r } - 3
- 2
2 \end{array} \right)$$

1. The point \(D\) is such that \(A B C D\) is a trapezium with \(\overrightarrow { D C } = 3 \overrightarrow { A B }\). Find the position vector of \(D\).
2. The diagonals of the trapezium intersect at the point \(P\). Find the position vector of \(P\).
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3. Using a scalar product, calculate angle \(A B C\).