// qdd on Feb 12, 2023

#ifdef qdd
#include <ringo>
#else
#include <bits/stdc++.h>
#define dbg(...)
#define dbgr(x, y)
#endif

using namespace std;

using ll = long long;

template <class T>
istream& operator>>(istream& is, vector<T>& v) {
  for (T& x : v) is >> x;
  return is;
}

template <class T>
ostream& operator<<(ostream& os, const vector<T>& v) {
  bool f = 0;
  for (const T& x : v) (f ? os << ' ' : os) << x, f = 1;
  return os;
}

void sol() {
  int n;
  ll V;
  cin >> n >> V;
  vector<ll> p(n), v(n);
  for (int i = 0; i < n; i++) {
    cin >> p[i] >> v[i];
  }
  double L = 0, R = 2.0001e12;
  auto check = [&](double x) {
    double left_max = -1e12, right_min = 1e12;
    for (int i = 0; i < n; i++) {
      if (p[i] == 0) {
        left_max = right_min = 0;
      } else if (p[i] < 0) {
        left_max = max(left_max, p[i] + x * v[i]);
      } else {
        right_min = min(right_min, p[i] - x * v[i]);
      }
    }
    return left_max >= right_min;
  };
  for (int _ = 0; _ < 150; _++) {
    double mid = (L + R) / 2;
    if (check(mid))
      R = mid;
    else
      L = mid;
  }
  cout << L * V << '\n';
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout << fixed << setprecision(10);
  int tt;
  cin >> tt;
  while (tt--) sol();
  return 0;
}