#include <bits/stdc++.h>

using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int tt;
  cin >> tt;
  while (tt--) {
    int n, v;
    cin >> n >> v;
    vector<int64_t> p(n), s(n);
    for (int i = 0; i < n; i++) {
      cin >> p[i] >> s[i];
    }
    const int64_t inf = int64_t(1e12);
    auto Check = [&](long double t) {
      long double L = -inf;
      long double R = inf;
      for (int i = 0; i < n; i++) {
        if (p[i] < 0) {
          L = max(L, p[i] + t * s[i]);
        } else {
          R = min(R, p[i] - t * s[i]);
        }
      }
      return L >= R;
    };
    int64_t limit = inf;
    for (int i = 0; i < n; i++) {
      limit = min(limit, (abs(p[i]) + inf + s[i] - 1) / s[i]);
    }
    long double low = 0, high = limit, t = 0;
    for (int iter = 0; iter < 200; iter++) {
      long double mid = (low + high) / 2;
      if (Check(mid)) {
        t = mid;
        high = mid - 1;
      } else {
        low = mid + 1;
      }
    }
    cout << fixed << setprecision(10) << t * v << '\n';
  }
  return 0;
}