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

\(\overrightarrow{OA} = 2\mathbf{i} + 3\mathbf{j} + 5\mathbf{k}\) and \(\overrightarrow{OB} = 7\mathbf{i} + 4\mathbf{j} + 3\mathbf{k}\).

1. Use a scalar product to find angle \(OAB\).
2. Find the area of triangle \(OAB\).