Find the sum of the given series:
(1) + (1+2) + (1+2+3) + ... + (1+2+3+...+10)​

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.