Let 'a' and 'b' be non collinear vectors of which 'a' is a unit vector. The angles of the triangle whose two sides are represented by  3( a x b ) and b-(a.b)a are

 

A) pie/2,pie/3,pie/3                                            B) pie/2,pie/4,pie/4                 C) pie/3,pie/3,pie/3                                            D) data insufficient