You roll one die. what is the probability that you roll a 6?
a) 1 /2
b) 1/ 4
c) 1 /6
d) 2/ 6

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.