#include<bits/stdc++.h>
using namespace std;
using ll = long long;
const int N = 1e5 + 5;
ll a, b, c;
void solve()
{
    cin>>a>>b>>c;
    ll now = 1, cur = 0, ans = 1e18;
    while(1)
    {
        ll res = cur + ((c+now-1)/(now))*b;
        ans = min(ans,res);
        if(now>=c) break;
        now <<= 1;
        cur += a;
    }
    cout<<ans<<'\n';
}
int main(void)
{
    ios::sync_with_stdio(0);
    cin.tie(0), cout.tie(0);
    int T = 1;
    cin >> T;
    while(T--) solve();
    return 0;
}