#include<bits/stdc++.h>
  
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
#define sz(a) ((int)a.size())
#define pb push_back
#define lson (rt << 1)
#define rson (rt << 1 | 1)
#define gmid (l + r >> 1)
const int maxn = 2e5 + 5;
const int inf = 0x3f3f3f3f;
const int mod = 1e9 + 7;
 
int a[maxn], b[maxn];
int n, m;

int main(){
 
    ios::sync_with_stdio(0); cin.tie(0);
    int t; cin >> t;
    while(t--){

        cin >> n >> m;
        for(int i = 1; i <= n; ++i){

            cin >> a[i] >> b[i];
        }
        int ret = inf;
        for(int i = 1; i <= n; ++i){

            ret = min(ret, (m + a[i] - 1) / a[i] * b[i]);
        }
        cout << ret << "\n";
    }
    return 0;
}