/*********************************************************************
    > File Name: 1.cpp
    > Author: yuki
 *********************************************************************/

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

typedef long long ll;

int main()
{
    int t;
    scanf("%d", &t);
    while(t--)
    {
        int n, m;
        scanf("%d%d", &n, &m);
        int x[105]={0}, y[105]={0};
        for(int i=1; i<=n; i++) scanf("%d%d", &x[i], &y[i]);
        int ans=INT_MAX;
        for(int i=1; i<=n; i++)
        {
            int tmp=m/x[i];
            if((m%x[i]) != 0) tmp++;
            int ttmp=tmp*y[i];
            ans=min(ans, ttmp);
        }
        printf("%d\n", ans);
    }
    return 0;
}