Referred to the origin \(O\), the points \(A\), \(B\) and \(C\) have position vectors given by
$$\overrightarrow{OA} = \mathbf{i} + 2\mathbf{j} + 3\mathbf{k}, \quad \overrightarrow{OB} = 2\mathbf{i} + 4\mathbf{j} + \mathbf{k} \quad \text{and} \quad \overrightarrow{OC} = 3\mathbf{i} + 5\mathbf{j} - 3\mathbf{k}.$$
- Find the exact value of the cosine of angle \(BAC\). [4]
- Hence find the exact value of the area of triangle \(ABC\). [3]
- Find the equation of the plane which is parallel to the \(y\)-axis and contains the line through \(B\) and \(C\). Give your answer in the form \(ax + by + cz = d\). [5]