#include<bits/stdc++.h>
#define ls ch[x][0]
#define rs ch[x][1]
#define ll long long
using namespace std;

inline ll read(){
    ll num=0,neg=1;char c=getchar();
    while(!isdigit(c)){if(c=='-')neg=-1;c=getchar();}
    while(isdigit(c)){num=(num<<3)+(num<<1)+c-'0';c=getchar();}
    return num*neg;
}

int T,n,m,ans;

int main(){
    T=read();
    while(T--)
    {
        n=read();m=read();ans=1e9;
        for(int i=1;i<=n;i++)
        {
            int x=read(),y=read();
            ans=min(ans,(m+x-1)/x*y);
        }printf("%d\n",ans);
    }return 0;
    
}