abstract class Shape { int a,b; public Shape(int aa, int bb) { a=aa; b=bb; } abstract public double area(); } class Rectangle extends Shape { public Rectangle(int aa, int bb) { super(aa,bb); } public double area() { return a*b; } } class Triangle extends Shape { public Triangle(int aa, int bb) { super(aa,bb); } public double area() { return a*b/2; } } public class XXK3 { public static void main(String[] args) { Shape x,y; x=new Rectangle(10,20); y=new Triangle(10,15); System.out.println(x.area()+", "+y.area()); } } 程序运行的结果是 ( )。