#include <bits/stdc++.h>
#define mst(a,b) memset(a,b,sizeof(a))
#define lowbit(x) ((x)&(-x))
#define X first
#define Y second
#define lc o<<1
#define rc o<<1|1
using namespace std;
typedef long long LL;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<double,double> pdd;
typedef pair<ll, ll> pll;
const int inf = 0x3f3f3f3f;
const ll INF = 0x3f3f3f3f3f3f3f3f;
const int maxn = 2000+10;
const int maxm = 100000+10;
const int mod = 1e9+7;
const double eps = 1e-8;

int main() {
#ifdef local
    freopen("in.txt", "r", stdin);
//    freopen("out.txt", "w", stdout);
#endif
    ios::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);
    int T; cin>>T;
    while (T--){
        int n,m; cin>>n>>m;
        int ans=inf;
        for (int i=0;i<n;i++){
            int x,y; cin>>x>>y;
            int k=m/x;
            if (m%x) k++;
            ans=min(ans,k*y);
        }
        cout<<ans<<"\n";
    }
    return 0;
}