6. Consider the parallelogram \( A B C D \) where \( A ( 0.1 .2 ) , B ( 1.2 .3 ) \) , and \( C ( 0.3 .5 ) \) .
[2] a) Find the coordinates of the vertex \( D \) .
[2] b) Find the angle \( \angle B \) .
[2] b) Find the area of the triangle \( \triangle A B C \) .