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;

}