(7-1)请阅读程序,写出程序运行结果。 class Base { int getN() { return 4; } } class Sub1 extends Base { int getN() { return 5; } } class Sub2 extends Base { int getN() { return 6; } } public class Demo5 { public static void main(String[] args ) { Base a = new Base(); Sub1 b = new Sub1(); Base c = new Sub1(); Base d = new Sub2(); System. out .println( a .getN() * b .getN() * c .getN() * d .getN()); } }