I need to calculate the projection of a 3D vector, but I don't know how. Could you please help me?

There are two 3D vectors:

**A**and

**B**.

**A**and

**B**are both on plane

**P**.

**L**is a line on

**P**, through the origin, and perpendicular to

**A**.

How do I calculate the vector

**C**which is the projection of

**B**on

**L**?

Thank you for your time!

Cornelis