#include <bits/stdc++.h>
#define LL long long

using namespace std;

void solve()
{
    LL a, b, c;
    cin >> a >> b >> c;

    LL ans = c * b;
    for (LL i = 2, j = 1; i <= (c << 1); i <<= 1, j++)
        ans = min(ans, j * a + (c + i - 1) / i * b);
    cout << ans << "\n";
}

int main()
{
    ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);

    int tt = 1;
    cin >> tt;
    while (tt--)
        solve();
}