(a) 20. let s be the suface of the cone z yx + y bounded by the planes z 0 and z- 3 further, let c be the closed curve forming the boundary of the surface s. a

(a) 20. Let S be the suface of the cone z yx + y bounded by the planes z 0 and z- 3 Further, let C be the closed curve forming the boundary of the surface S. A vector field such that Vx F= -Xi - yj. The absolute value of the line integral F dr, where r= xi +yj +zk andr = |r|, is (a) 0 (b) 97 (c) 15 (d) 18r