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

inline int read(){
    int x=0,f=1;char cc=getchar();
    while(cc<'0' || cc>'9') {if(cc=='-') f=-1;cc=getchar();}
    while(cc>='0' && cc<='9') {x=x*10+cc-'0';cc=getchar();}
    return x*f;
}

int main(){
    for(int tt=read();tt;tt--){
        int n=read();int m=read();
        int ans=2000000000;
        for(int i=1;i<=n;i++){
            int x=read();int y=read();
            int z=m/x;
            if(z*x<m) z++;
            ans=min(ans,y*z);
        }
        printf("%d\n",ans);
    }
}