#include <bits/stdc++.h>
using std::cin;
using std::cout;
using std::endl;
using std::set;
using std::map;
using std::min;
using std::max;
using std::vector;
using std::deque;
using std::min;
using std::max;
using std::swap;
using std::string;
typedef long long ll;
typedef double db;
const int MOD = 998244353;
const int N = 100005;
ll power(const ll & x,const ll & mi)
{
    ll s1=1LL,s2=x,m=mi;
    while (m)
    {
        if (m&1) s1=s1*s2%MOD;
        s2=s2*s2%MOD;
        m>>=1;
    }
    return s1;
}
void solve()
{
    ll ans=1e18;
    int n,m;
    int x,y;
    cin>>n>>m;
    for (int i=1;i<=n;++i)
    {
        scanf("%d%d",&x,&y);
        int t=(m-1)/x+1;
        ans=min(ans,1LL*t*y);
    }
    cout<<ans<<endl;
    return;
}
int main()
{
    int T=1;
    cin>>T;
    while (T--) solve();
    return 0;
}