#include <cstdio>
#include <cstring>
#include <cmath>
#include <iostream>
#include <algorithm>
#include <vector>
#include <stack>
#include <sstream>
#include <map>
#include <set>
#include <string>
using namespace std;

typedef long long ll;
const int inf=0x3f3f3f3f;
#define mem(a,b) memset(a,b,sizeof(a))
int main()
{
    int t,n,m,x,y,tmp,ans,sum;
    scanf("%d",&t);
    while(t--)
    {
        sum=inf;
        scanf("%d %d",&n,&m);
        for(int i=1;i<=n;++i)
        {
            tmp=0;
            scanf("%d %d",&x,&y);
            if(m%x!=0)tmp++;
            tmp+=m/x;
            ans=tmp*y;
            sum=min(sum,ans);
        }
        printf("%d\n",sum);
    }
    return 0;
}