#include <bits/stdc++.h>
using namespace std;

const int N = 4010;
const int M = 100100;
#define inf 0x3f3f3f3f
typedef long long ll;

ll f[M];
int _;
int main()
{
    for (scanf("%d", &_); _; _ --)
    {
        int n, m;
        scanf("%d%d", &n, &m);
        int u, v;
        int ans = inf;
        for (int i = 1; i <= n; i ++)
        {
            scanf("%d%d", &u, &v);
            ans = min(ans, (m + u - 1) / u * v);
        }
        cout << ans << '\n';
            
    }
}