(a) Use Gauss' Theorem to calculate F ds where: F (3x², xy, z) and S = {(x, y, z)x+y+z≤1 and 0 < x, y, z} (b) Calculate F. ds where F = 3xy²i+3x²yj+z³k and S is the unit sphere with the outward pointing normal n(x, y, z) = (x, y, z).