#include <bits/stdc++.h>
#include <ext/random>

using namespace std;

#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define sz(v) (int)(v).size()

typedef long long ll;
typedef pair<int, int> pii;

__gnu_cxx::sfmt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

template<typename T>
std::ostream& operator << (std::ostream& os, const vector<T>& a) {
    for (const T& x : a) {
        os << x << ' ';
    }
    return os;
}


int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int t;
    cin >> t;
    while (t--) {
        int n;
        double V;
        cin >> n >> V;
        vector<double> p(n), v(n);
        for (int i = 0; i < n; ++i) {
            cin >> p[i] >> v[i];
        }
        double low = 0, high = 1e12;
        for (int it = 0; it < 100; ++it) {
            double mid = (low + high) / 2;
            double maxL = -1e12;
            double minR = 1e12;
            for (int i = 0; i < n; ++i) {
                if (p[i] < 0) {
                    maxL = max(maxL, p[i] + mid * v[i]);
                } else {
                    minR = min(minR, p[i] - mid * v[i]);
                }
            }
            if (maxL < minR) {
                low = mid;
            } else {
                high = mid;
            }
        }
        cout.precision(15);
        cout << low * V << '\n';
    }

    return 0;
}