Three points A, B and C have coordinates (2,1,-2), (2,-1,-1) and (1,2,2) respectively. The vectors OA, OB and OC where O is theorigin form three concurrent edges of a parallelepiped OAPBCQSR in the diagram:

http://i45.tinypic.com/1ordkp.jpg

1. Find the coordinates of P, Q, R and S

2. Fina an equation for the plan OAPB

3. calculate the volume, B or the parallelepiped

Any help appreciated, im not sure where to start for Q1 and Q2

Thanks