Amy found a Homecoming dress at the mall. It was on sale for $215. If the tax rate is 8.25%, what was final amount that she paid?

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.