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(5,8);
y=new Triangle(5,8);
System.out.println(x.area()+", "+y.area());
}
}

【A.】40.0, 20.0
【B.】80.0, 40.0

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