#include <bits/stdc++.h>
#define LL long long
#define PII pair<int,int>
#define mp make_pair
#define fi first
#define se second
using namespace std;
const int maxn = 1e5+10;




int n,m,x,y;
void work(){
    cin>>n>>m;
    int ans = 100000000;
    while (n--){
        cin>>x>>y;
        int tmp = (m + x - 1) / x * y;
        if (tmp < ans) ans = tmp;
    }
    cout<<ans<<endl;
}
void vgeler(){
    int test;
    cin>>test;
    while (test--) work();
}
int main(){
    vgeler();
    return 0;
}