#include<bits/stdc++.h>
using namespace std;
int main(){
    int T; scanf("%d",&T);
    while(T--){
        int n,m; scanf("%d %d",&n,&m);
        int ans = 0x3f3f3f3f;
        for(int i = 1;i<=n;++i){
            int x,y; scanf("%d %d",&x,&y);
            int tem = m/x;
            if(m%x) ++tem;
            ans = min(ans,tem*y);
        }
        printf("%d\n",ans);
    }
}