#include<bits/stdc++.h>
using namespace std;
const int N=105,M=10200;
int n,m,f[M+5],ans;
void Mi(int &x,int y){if(x>y && (x=y));}
void Clear(){
    ans=1e9;
}
void solve(){
    Clear();
    scanf("%d%d",&n,&m);
    for(int i=1,x,y;i<=n;++i){
        scanf("%d%d",&x,&y);
        int tmp=(m-1)/x+1;
        Mi(ans,tmp*y);
    }
    printf("%d\n",ans);
}
int main(){
    int t;scanf("%d",&t);
    for(;t;--t)solve();
    return 0;
}