#include<iostream>
#include<cstdio>
#include<vector>
#include<stack>
#include<queue>
#include<set>
#include<map>
#include<cstring>
#include<string>
#include<cmath>
#include<algorithm>
#define LL long long
#define PII pair<int,int>
#define pi acos(-1.0)
#define lowbit(x) x&(-x)
using namespace std;

int T,n,m;

int main(void){
    scanf("%d",&T);
    while(T--){
        scanf("%d %d",&n,&m);
        int ans=2e9+10;
        for(int i=1;i<=n;i++){
            int x,y;
            scanf("%d %d",&x,&y);
            int t=m/x;
            if(m%x) t++;
            ans=min(ans,y*t);
        }
        printf("%d\n",ans);
    }
    return 0;
}