Please help me understand this in as much detail as possible. Thank you.

It is for intermediate calculus

9. Find the x-coordinate x of the center of mass of the solid in the first octant bounded by the plane 2x + 4y + z = 8 if the density function p(x, y) = z + 1. (5 pts) 10.(a) Find a function whose gradient field is F(x,y) = (2y - - 1 (x+1)2 , 2x + 2y). (b) Use your answer to (a) and the Fundamental Theorem of Line Integrals to find S (2y - 1 (x+ 1) 2 ) dx + (2x + 2y) dy, where C is the curve y = 4 cos- x from (1, 2) to (0, 4). (5 pts)