#include<iostream>
#include<stdio.h>
#include<cstdio>
#include<vector>
#include<algorithm>
#include<cstring>
#include<cmath>
#include<queue>
#include<string>
#include<stack>
#include<set>
#include<map>
#include<bitset>
//#include<unordered_map>
#include<time.h>
#include<cstdlib>
typedef long long ll;
//#pragma comment(linker, "/STACK:1024000000,1024000000")
#define mm(a) memset(a,0,sizeof(a))
#define lr rt<<1
#define rr rt<<1|1
#define sync std::ios::sync_with_stdio(false);std::cin.tie(0);
#define inf 0x3f3f3f3f
//#define eqs 1e-8
#define lb(x) (x&(-x))
#define ch(a) (int(a-'a')+1)
#define rep(i,a,b) for(int i=a;i<=b;i++)
#define mkp(a,b) make_pair(a,b)
using namespace std;
typedef pair<int,int> pii;
const double pi=acos(-1);
const int maxn=20010;
//const ll Mod=1000000007;
const ll Mod=998244353;
 


 int main()
{
    sync;
    int n;
    int t;
    int m;
    cin>>t;
    while(t--)
    {
        cin>>n>>m;
        int mx=2e9;
        int k,x,y;
        for(int i=1;i<=n;i++)
        {
            cin>>x>>y;
            k=m/x;
            if(m%x)
                k++;
            mx=min(k*y,mx);
        }
        cout<<mx<<endl;
    }
    
    return 0;
}