Evaluate (x - y) dA where R = {(x, y) : 4 ≤ x² + y² ≤ 16 and y ≤ x} R 6. Evaluate ffe e-(x² + y²) dA where R = {(x, y) : x² + y² ≤ 3 and 0 ≤ y ≤ √√3x} R 7. Use a double integral in polar coordinates to calculate the area of the region which is inside of the cardioid r = 2 + 2 cos 0 and outside of the circle r = = 3.