#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using Int = __int128;

#ifdef LOCAL
#include "debug.h"
#else
#define debug(...) 2137
#endif

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  int tt;
  cin >> tt;
  while (tt--) {
    int n, v;
    cin >> n >> v;
    vector<pair<ll, ll>> a, b;
    for (int i = 0; i < n; i++) {
      ll p, vv;
      cin >> p >> vv;
      (p > 0 ? a : b).push_back({vv, abs(p)});
    }
    auto cmp = [&] (auto x, auto y) {
      return (Int)x.first * y.second - (Int)x.second * y.first > 0;
    };
    int p1 = min_element(a.begin(), a.end(), cmp) - a.begin();
    int p2 = min_element(b.begin(), b.end(), cmp) - b.begin();
    ld t = ld(a[p1].second + b[p2].second) / (a[p1].first + b[p2].first);
    cout << fixed << setprecision(10) << t * v << '\n';
  }
}