question_answer

If \[\mathbf{a}=\mathbf{i}-\mathbf{j}+\mathbf{k},\,\,\mathbf{b}=\mathbf{i}+2\mathbf{j}-\mathbf{k}\] and \[\mathbf{c}=3\mathbf{i}+p\mathbf{j}+5\mathbf{k}\] are coplanar then the value of p will be     [RPET 1985, 86, 88, 91]

A)             ? 6

B)             ? 2

C)             2

D)             6