#include <iostream>
#include <cstdio>
#include <cstdlib>

using namespace std;

int n, m, ans;
const int INF = 0x7fffffff;

void work()
{
    cin >> n >> m;
    ans = INF;
    for (int i = 1; i <= n; i++) {
        int x, y;
        cin >> x >> y;
        ans = min(ans, (m + x - 1) / x * y);
    }
    cout << ans << endl;
}

int main()
{
    ios::sync_with_stdio(false);
    int T;
    cin >> T;
    while (T--)
        work();

    return 0;
}