# Please help with this vector question

The points A, B and C have position vectors a=(2,1,2) b=(-3,2,5) and c=(4,5,-2) respectively, with respect to a fixed origin. The point D is such that ABCD, in >that order, is a parallelogram.

1. Find the position vector of D
2. Find the position vector of the point at which the diagonals of the >parallelogram intersect.
3. Calculate the angle BAC, giving your answer to the nearest tenth of a degree.
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Have you drawn it? –  Berci Oct 10 '12 at 1:16
$a,b,c$ determine a plane. So you work on this plane. –  Sigur Oct 10 '12 at 1:41
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