c++ 类与对象应用题

#include<bits/stdc++.h>
using namespace std;
class tank
{
    private:
        int F;
        int vin;
        int vout;
        int gravity;
    public:
        tank():F(0),vin(0),vout(0),gravity(0){    }
        ~tank(){
		};
        void set(int f,int in,int out)
        {
            F=f;
            vin=in;
            vout=out;
        }
        int getin(int t0,int te)
        {
            gravity+=(te-t0)*vin;
            return gravity;
        }
        int getout(int t0,int te)
        {
            gravity-=(te-t0)*vout;
            if(gravity<=0)
            {
                gravity=0;
            }
               return gravity;
        }
        int getresult()
        {
            if(gravity<F)
            {
                return gravity;
            }
            else
            {
                return F;
            }
        }
}; 
int main()
{
    tank t1;
    t1.set(10000,200,160);
    tank t2;
    t2.set(5000,150,100);
    tank t3;
    t3.set(5000,100,120);
    t1.getin(0,30);
    t2.getin(20,50);
    t3.getin(40,50);
    t3.getout(60,70);
    t1.getout(60,80);
    int res=t1.getresult()+t2.getresult()+t3.getresult();
    cout<<res;
    return 0;
    
}