#include <cassert>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <functional>
#include <iostream>
#include <limits>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

using Int = long long;

template <class T1, class T2> ostream &operator<<(ostream &os, const pair<T1, T2> &a) { return os << "(" << a.first << ", " << a.second << ")"; };
template <class T> ostream &operator<<(ostream &os, const vector<T> &as) { const int sz = as.size(); os << "["; for (int i = 0; i < sz; ++i) { if (i >= 256) { os << ", ..."; break; } if (i > 0) { os << ", "; } os << as[i]; } return os << "]"; }
template <class T> void pv(T a, T b) { for (T i = a; i != b; ++i) cerr << *i << " "; cerr << endl; }
template <class T> bool chmin(T &t, const T &f) { if (t > f) { t = f; return true; } return false; }
template <class T> bool chmax(T &t, const T &f) { if (t < f) { t = f; return true; } return false; }


using Double = long double;
constexpr Double INF = 1e+30;

int N;
Int U;
vector<Int> P, V;

int main() {
  for (int numCases; ~scanf("%d", &numCases); ) { for (int caseId = 1; caseId <= numCases; ++caseId) {
    scanf("%d%lld", &N, &U);
    P.resize(N);
    V.resize(N);
    for (int i = 0; i < N; ++i) {
      scanf("%lld%lld", &P[i], &V[i]);
    }
    
    Double lo = 0.0, hi = 1e+15;
    for (int iter = 0; iter < 100; ++iter) {
      const Double mid = (lo + hi) / 2;
      Double mxL = -INF;
      Double mnR = +INF;
      for (int i = 0; i < N; ++i) {
        if (P[i] < 0) {
          chmax(mxL, P[i] + V[i] * mid);
        } else {
          chmin(mnR, P[i] - V[i] * mid);
        }
      }
      ((mxL >= mnR) ? hi : lo) = mid;
    }
    const Double ans = U * hi;
    printf("%.12Lf\n", ans);
  }
#ifndef LOCAL
  break;
#endif
  }
  return 0;
}