Relative to an origin O, the position vectors of the points A, B and C are given by

\(\overrightarrow{OA} = \begin{pmatrix} 2 \\ -1 \\ 4 \end{pmatrix}, \quad \overrightarrow{OB} = \begin{pmatrix} 4 \\ 2 \\ -2 \end{pmatrix} \quad \text{and} \quad \overrightarrow{OC} = \begin{pmatrix} 1 \\ 3 \\ p \end{pmatrix}.\)

Find

(i) the unit vector in the direction of \(\overrightarrow{AB}\),

(ii) the value of the constant \(p\) for which angle \(BOC = 90^\circ\).