#include<bits/stdc++.h>
using namespace std;
#define int long long
void solve(){
	int a,b,c;
	cin>>a>>b>>c;
	int ans=1e18;
	int cur=0;
	int sz=1;
	for(int i=0; i<33; i++){
		int t=c/sz;
		if(c%sz!=0) t++;
		ans=min(ans,cur+t*b);
		sz*=2;
		cur+=a;
	}
	cout<<ans<<endl;
}
signed main(){
	ios::sync_with_stdio(0);
	cin.tie(NULL);
	cout.tie(NULL);
	int t=1;
	cin>>t;
	while(t--) solve();
}