#include <bits/stdc++.h>

using namespace std;

#define ll long long

const int mod = 998244353;
const int inf = 1e8;

void solve() {
  ll a, b, c;
  cin >> a >> b >> c;
  ll ans = 1e18;
  ll f = 1, pre = 0;
  while (f <= c) {
    ans = min(ans, pre + ((ll)(c / f) + (c % f != 0)) * b);
    pre += a;
    f *= 2;
  }
  ans = min(ans, pre + ((ll)(c / f) + (c % f != 0)) * b);
  cout << ans << "\n";
}

signed main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cout << fixed << setprecision(10);
  int t = 1;
  cin >> t;
  while (t--) solve();
  return 0;
}