Equation of line passing through B and parallel to OA×OB is given by r‌‌=4i+k+λ(2i+11j−3k) ‌‌=(4+2λ)i+11λj+(1−8λ)k
since distance of line from point B is √189 √189‌‌=√(4+2λ−4)2+(11λ)2+(1−8λ−1)2 189‌‌=4λ2+121λ2+64λ2 189‌‌=189λ2 λ‌‌=±1 Therefore, r=6i+11j−7k