#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main() {
  ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  int T;
  cin >> T;
  while(T--) {
    ll a, b, c, ans = 1e18;
    cin >> a >> b >> c;
    for(int i = 0; i <= 30; i++) {
      ans = min(ans, i * a + (((c - 1) >> i) + 1) * b);
    }
    cout << ans << "\n";
  }
  return 0;
}