#include <bits/stdc++.h>
#include <iostream>
#include <algorithm>
#include <stdio.h>
const int Max = 100 * 100 * 100 + 5;
#define LL long long
LL mod = 1e9+7;
const int INF = 1e5;
//const int inx = INT_MAX;
using namespace std;
//  srand(time(NULL));
//      m = rand() % 1000 + 1;
//定义i i(A) i+n i+n(B) i+n+n i+n+n(C)
//bitset<Max>s,q;
//int a[100],n;

int main()
{
    int i,j,t,a[105],b[105],n,m;
    cin >> t;
    while(t--){
        cin >> n >> m;
        for(i = 1; i <= n; i++) cin >> a[i] >> b[i];
        for(i = 1; i <= n; i++){
            if(m % a[i] == 0){
                a[i] = m / a[i];
                b[i] = a[i] * b[i];
            }
            else {
                a[i] = m / a[i] + 1;
                b[i] = a[i] * b[i];
            }
        }
        int ans = 100000000;
        for(i = 1; i <= n; i++){
            ans = min(ans,b[i]);
        }
        cout << ans << endl;
    } 
    return 0;    
}