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

const int INF = 0x3f3f3f3f;
const int N = 110;
int T, n, m;

struct node
{
    int x, y;
}p[N];

int main()
{
    cin >> T;
    while(T --)
    {
        cin >> n >> m;

        for(int i = 0; i < n; i ++)
            scanf("%d%d", &p[i].x, &p[i].y);

        int ans = INF, temp;
        for(int i = 0; i < n; i ++)
        {
            if(m % p[i].x) temp = m / p[i].x + 1;
            else temp = m / p[i].x;

            ans = min(ans, temp * p[i].y);
        }

        cout << ans << endl;
    }

    return 0;
}