使用VC6打开考生文件夹下的工程test17_1，此工程包含一个源程序文件test17_1．唧，但该程序运行有问题，请改正程序中的错误，使程序的输出结果如下：
Vehicle message
Car message
Vehicle message
源程序文件test17_1.cpp 清单如下:
include ＜iostream.h＞
class vehicle
{
int wheels;
float weight;
public:
/***************** found *****************/
void message(void){ cout＜＜"Vehicle message\n";}
};
class car:public vehicle
{
int passenger_load;
public:
/***************** found *****************/
void message (void){cout＞＞"Car message\n";}
};
class truck:public vehicle
{
int passenger_load;
float payload;
public:
int passengers(void){return passenger_load;}
};
void main()
{
vehicle * unicycle;
unicycle=new vehicle;
/***************** found *****************/
unicycle.message()
delete unicycle;
unicycle=new car;
unicycle-＞message();
delete unicycle;
unicycle=new truck;
unicycle-＞message();
delete unicycle;
}