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

public:
Student(int xx)x=xx;
virtual float calcFuition( );
protected:
int x;

float Student:: calcTuition()

return float(x* x)
class GraduateStudent:public Student

public:
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