#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<vector>
#include<stdlib.h>
#include<queue>
#include<set>
#include<map>
#include<iomanip>
#include<math.h>
using namespace std;
typedef long long ll;
const int inf = 0x3f3f3f3f;
int i,j,k;
int n,t,m;
int x,y;
int res,cnt,temp,sum;
int v[110],w[110];
int main(){
    int t;scanf("%d",&t);
    while(t--){
        int ans = inf;
        scanf("%d%d",&n,&m);
        for(int i = 1,x,y;i <= n;i++){
            scanf("%d%d",&x,&y);
            int cnt = (m + x - 1)/x;
            ans = min(ans,cnt * y);
        }
        printf("%d\n",ans);
    }
    return 0;
}