/***************************************************************
    File name: a.cpp
    Author: huhao
    Create time: Sun 19 Jul 2020 02:02:40 PM CST
***************************************************************/
#include<stdio.h>
#include<string.h>
#include<math.h>
#include<algorithm>
#define fr(i,a,b) for(int i=(a),end_##i=(b);i<=end_##i;i++)
#define fd(i,a,b) for(int i=(a),end_##i=(b);i>=end_##i;i--)
int read()
{
    int r=0,t=1,c=getchar();
    while(c<'0'||c>'9')
    {
        t=c=='-'?-1:1;
        c=getchar();
    }
    while(c>='0'&&c<='9')
    {
        r=r*10+c-48;
        c=getchar();
    }
    return r*t;
}
const int N=100010,inf=123456789;
int n,m,ans;
int main()
{
    fr(T,1,read())
    {
        n=read(); m=read(); ans=inf;
        fr(i,1,n)
        {
            int a=read(),b=read();
            ans=std::min(ans,(m+a-1)/a*b);
        }
        printf("%d\n",ans);
    }
    return 0;
}