Look at triangle abc. what is the length of side ab of the triangle?

a) 3
b) 5
c) √6
d) √13

Use stokes' theorem to evaluate c f · dr where c is oriented counterclockwise as viewed from above. f(x, y, z) = xyi + 5zj + 7yk, c is the curve of intersection of the plane x + z = 8 and the cylinder x2 + y2 = 81.