19. A.The first Quadrant 
B.The fourth Quadrant and the coordinates are (5,-3)
C. The third Quadrant and the coordinates are (-5,-3)
20. Yes, it is! It has a curve that will allow the plane to navigate and to fly by allowing air to push up on it. 
21. 1st quadrant +x +y
 : 2nd qudrant -x +y 
: 3rd quadrant -x -y 
: 4th quadrant +x -y