For every two-dimensional set C contained in R² for which the integral exists, let Q(C) = ∫ ∫_C(x² + y²) dxdy. If C₁ = {(x, y) : −1 ≤ x ≤ 1,−1 ≤ y ≤ 1}, C₂ = {(x, y) : −1 ≤ x = y ≤ 1}, and C₃ = {(x, y) : x²+y² ≤ 1}, find Q(C₁),Q(C₂), and Q(C₃).