Solve and get brainliest!!
please be sure of your answer​

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.

Use the method of cylindrical shells to find the volume v generated by rotating the region bounded by the given curves about y = 8.8y = x3, y = 0, x = 4use the method of cylindrical shells to find the volume v generated by rotating the region bounded by the given curves about y = 8.8y = x3, y = 0, x = 4

Aski resort is charging $37.50 to rent a snowmobile for 5 hours. at this rate what will be the cost for a family of 5 to rent snowmobiles for 3 hours on the first day of their vacation and 4 hours for on the last day of their vacation