#include<bits/stdc++.h>
using namespace std;
template<class T> void gi(T& ret){
    ret=0; char c=getchar(); int f=1;
    for(;c<'0'||c>'9';c=getchar())
        if(c=='-') f=-1;
    for(;c>='0'&&c<='9';c=getchar())
        ret=ret*10+(c-'0');
    ret*=f;
}
int main(){
    int T; gi(T);
    while(T--){
        int n,m; gi(n); gi(m);
        int ans=(int)2e9;
        for(int i=1;i<=n;++i){
            int x,y; gi(x); gi(y);
            ans=min(ans,((m-1)/x+1)*y);
        }
        printf("%d\n",ans);
    }
    return 0;
}