Evaluate the following iterated integrals
(a) ∫∫ xy x∈ [0,1],y∈ [0,y]dx dy
(b) ∫∫ y2y∈ [1,4], x∈[a,√x]dx dy
(c) ∫∫ 1dx x∈ [1,4] y ∈ [y2/2,√y] dx dy
(d) ∫∫ x2/y2x∈[1,2] y ∈ [1,x] dy dx
(e) ∫∫ y/ex y∈ [0,1] x ∈ [0,x] dydx
(f) ∫∫ xcosy y ∈[0,π/2] x ∈ [0,x2] dydx
