class line; class box private: int color; int upx,upy; int lowx,lowy; public: ______ void set_color(int c)color=c; void define_box(int x1,int y1,int x2,int y2) upx=x1;upy=y1;lowx=x2;lowy=y2; ; class line private: int color; int startx,starty; int endx,endy; public: friend int same_color(line l,box b); void set_color(int c)color=c; void define_line(______) startx=x1;starry=y1;endx=x2;endy=y2; ; int same_color(line l,box b) if(l.color==B、color)return 1; return 0;