#include<bits/stdc++.h>
#include<ext/pb_ds/tree_policy.hpp>
#include<ext/pb_ds/assoc_container.hpp>
#define ll long long
#define int long long
using namespace std;

const int maxn = 310000;

int calc(int Cp,int Cm,int D1,int N,int T)
{
	if(N<0) return 0;
	
	int ret=0;
	
	ret=max(ret, Cp*max(1ll, N-D1)*T );
	int tk= (Cm*N-Cp)/(2*Cm);
	if(tk<0) tk=0;
	if(tk>T) tk=T;
	for(int k=tk-2;k<=tk+2;k++)
	{
		if(k>=0 && k<=T)
			ret=max(ret, Cp*(T-k)+Cm*(N-k)*k);
	}
	return ret;
}

signed main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	
	int Tcase; cin>>Tcase;
	while(Tcase--)
	{
		int Cp,Cm,H0,A1,D1,N;
		cin>>Cp>>Cm>>H0>>A1>>D1>>N;
		
		int ans=0;
		if(A1>=H0)
		{
			ans= max( Cp*max(1ll,N-D1),Cm*(N-1) );
			
			N-=A1-H0;
			A1=H0;
		}
		for(int l=1;l<=H0;l++)
		{
			int r= H0/(H0/l);
			
			int use= A1-min(A1,r);
			ans=max(ans, calc( Cp,Cm,D1,N-use,H0/r ) );
			
			l=r;
		}
		cout<<ans<<'\n';
	}
	
	return 0;
}