18. a current carrying loop lying in the plane of the paper is in the shape of an equilateral triangle of side a. it carries a current i in the clockwise sense

18. A current carrying loop lying in the plane of the paper is in the shape of an equilateral triangle of side a. It carries a current I in the clockwise sense as viewed from above. If k denotes the outward normal to the plane of the paper, the magnetic moment m due to the Current loop is (A) m-a1k (B) m--%aik (C) m--a'k (D) m--ak