Help please!

The points A, B, C have position vectors i + j + 2k, i + 2j + 3k, 3i + k respectively and lie in plane π.

1. Find the area of triangle ABC

2. the shortest distance from C to the line AB

3. the cartesian equation of the plane π

The line L passes through the origin and is normal to the plane π, it intersects π at the point D.

4. Find the coordinates of the point D

5. The distance of π from the origin

Thank you!