#include <bits/stdc++.h>
using namespace std;
const int maxn=11234;
int cas,n,m,res,x[105],y[105];
int main()
{
    cin>>cas;
    while (cas--) {
        scanf("%d%d",&n,&m);
        for (int i=1;i<=n;++i) scanf("%d%d",&x[i],&y[i]);
        int res=0x3f3f3f3f;
        for (int i=1;i<=n;++i) res=min(res,(m+x[i]-1)/x[i]*y[i]);
        printf("%d\n",res);
    }
    return 0;
}