#include <bits/stdc++.h>
using namespace std;

#define int long long


void doit(){
	int a,b,c,ans=2e18;
	cin>>a>>b>>c;
	for(int i=1,t=0;;t++,i*=2){
		ans=min(ans,t*a+((c-1)/i+1)*b);
		if(i>c) break;
	}
	cout<<ans<<endl;
}

signed main(){
	ios::sync_with_stdio(0);
	int t;
	cin>>t;
	while(t--) doit();
}