#include <bits/stdc++.h>
using namespace std;
using namespace chrono;

using ll = long long;
using ull = unsigned long long;

string to_string(const string &s) {
  return '"' + s + '"';
}

string to_string(bool b) {
  return b ? "true" : "false";
}

template <typename A, typename B>
string to_string(const pair<A, B> &p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

template <typename T>
string to_string(const T &v) {
  string s = "{";
  bool first = true;
  for (const auto &it : v) {
    if (!first)
      s += ", ";
    else
      first = false;
    s += to_string(it);
  }
  return s += "}";
}

void debug_out() {
  cerr << endl;
}

template <typename T, typename... Args>
void debug_out(const T &first, const Args&... rest) {
  cerr << to_string(first) << " ";
  debug_out(rest...);
}

#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

auto startTime = high_resolution_clock::now();
int get_time() {
  auto stopTime = chrono::high_resolution_clock::now();
  auto duration = duration_cast<milliseconds>(stopTime - startTime);
  return duration.count(); // in ms
}

void solve() {
  int n, v;
  cin >> n >> v;

  vector<pair<ll, ll>> al, ar;
  for (int i = 1; i <= n; ++i) {
    ll x, y;
    cin >> x >> y;
    if (x < 0)
      al.push_back({y, x});
    else
      ar.push_back({-y, x});
  }

  long double st = 0, dr = 1e12;
  int steps = 128;
  while (steps--) {
    long double mij = (st + dr) / 2.0;

    long double l = -1e12;
    for (auto it : al)
      l = max(l, it.first * mij + it.second);

    long double r = 1e12;
    for (auto it : ar)
      r = min(r, it.first * mij + it.second);

    //cout << l << " " << r << " " << mij << endl;
    if (l > r)
      dr = mij;
    else
      st = mij;
  }

  cout << fixed << setprecision(20) << dr * v << endl;
}

int main() {
  cin.tie(NULL);
  ios_base::sync_with_stdio(false);

  int t = 1;
  cin >> t;
  while (t--)
    solve();

  return 0;
}