下列程序的执行结果是 【12】 。#include＜iostream. h＞clas

问题：

下列程序的执行结果是 【12】 。
#include＜iostream. h＞
class Studentpublic:
Student(int xx)x=xx;
virtual float calcFuition( );
protected:
int x;float Student:: calcTuition() return float(x* x)
class GraduateStudent:public Studentpublic:
GraduateStudent(int xx) :Student(xx)
float calcTuition( )
;
float GraduateStudent:: calcTuition( ) return float(x * 2);void main( ) Student s(20);
GraduateStudent gs(30);
cout＜＜s.calcTuition()＜＜" "＜＜gs. calcTuition()＝＝end1;
//计算学生s和研究生gs的学费