#include<iostream>
#include<cstring>
#include<algorithm>
#include<cstdio>
#include<cmath>
#include<map>
#include<queue>
#include<vector>
#define ll long long
#define PI acos(-1.0)
#define F first
#define S second
#define pb push_back
#define debug(x); printf("debug%d\n",x);
#define des(x); printf("des:%s\n",x+1);
#define rep(f,t) for(int i=f;i<=t;i++)
const ll INF=0x3f3f3f3f3f3f3f3f;
const int inf=0x3f3f3f3f;
const int mod=998244353;
using namespace std;
int t;
int n,m;
struct node
{
    int a,b;
    double x;
}q[110];
bool cmp(node c,node d)
{
    return c.x>d.x;
}
int main()
{
    scanf("%d",&t);
    while(t--)
    {
        int ans=inf;
        scanf("%d%d",&n,&m);
        for(int i=1;i<=n;i++)
        {
            scanf("%d%d",&q[i].a,&q[i].b);
            int temp=m/q[i].a;
            if(m%q[i].a)
            {
                temp++;
            }
            ans=min(ans,temp*q[i].b);
        }
        printf("%d\n",ans);

    }
    return 0;
}