3. For each of the following, evaluate JE f(x) dx.

(a) f(x,y) = xVfj and E is bounded by y = x and y = x2.

(b) f(x, y) = x + y and E is the triangle with vertices (0,0), (0,1), (2,0).

(c) f(x, y) = x and E is bounded by y = ,;x, x = -Vfj, and y = 4.

(d) f(x, y, z) = x and E is the set of points (x, y, z) such that 0 :::; z :::; 1 - x2, o :::; Y :::; x2 + z2, and x 2: o.