#include using namespace std; ? class car; class boat{ private: int weight; public: boat(int w){weight = w;} friend int gettotalweight(boat &b, car &c); }; ? class car{ private: int weight; public: car(int w){weight = w;} friend int gettotalweight(boat &b, car &c); }; ? int gettotalweight(boat &b, car &c){ return b.weight+c.weight; } int main() { boat b1(5); car c2(2); cout<<"Totalweight："<