#include <iostream>
using namespace std;

int main() {
  ios::sync_with_stdio(false);

  int test;
  cin >> test;
  while(test--) {
    int n, m;
    cin >> n >> m;
    int ans = 1e9;
    while(n--) {
      static int x, y;
      cin >> x >> y;
      int t = (m - 1) / x;
      int tmp = (t + 1) * y;
      ans = min(ans, tmp);
    }
    cout << ans << '\n';
  }
  return 0;
}