#define _CRT_SECURE_NO_WARNINGS
#pragma GCC optimize ("unroll-loops")
#pragma GCC optimization("O3")
#include <iostream>
#include <vector>
#include <string>
#include <set>
#include <map>
#include <iomanip>
#include <algorithm>
#include <iterator>
#include <stack>
#include <queue>
#include <unordered_set>
#include <unordered_map>
#include <stdio.h>
#include <math.h>
#include <bitset>
#include <numeric>
#include <deque>
#include <list>
#include <bitset>
#include <array>
#include <tuple>
#include <sstream>
#include <functional>
#include <cmath>
#include <random>
#include <cstring>
#include <fstream>
#include <stdexcept>
using namespace std;

#define pb push_back
#define mp make_pair
#define ifor(a, b) for(int i = a; i < b; ++i)
#define jfor(a, b) for(int j = a; j < b; ++j)
#define kfor(a, b) for(int k = a; k < b; ++k)
#define irof(a, b) for(int i = b - 1; i >= a; --i)
#define jrof(a, b) for(int j = b - 1; j >= a; --j)
#define krof(a, b) for(int k = b - 1; k >= a; --k)
#define all(a) (a).begin(), (a).end()

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<long long, long long> pll;

const ll MOD = 998244353;

ll mmod(ll x, ll y = MOD) {
    if (x >= 0)
        return x % y;
    return (y - ((-x) % y)) % y;
}


template <ll T = MOD>
struct Res {
    ll value;
    Res() : value(0) {}
    Res(ll val) : value(mmod(val, T)) {}
    Res& operator=(ll val) {
        value = mmod(val, T);
        return *this;
    }
    Res operator+(const Res<T>& other) const {
        return Res(mmod(value + other.value, T));
    }
    Res operator-(const Res<T>& other) const {
        return Res(mmod(value - other.value, T));
    }
    Res operator*(const Res<T>& other) const {
        return Res(mmod(value * other.value, T));
    }
    Res operator+(const Res<T>&& other) const {
        return Res(mmod(value + other.value, T));
    }
    void operator+=(const Res<T>& other) {
        value = mmod(value + other.value, T);
    }
    void operator-=(const Res<T>& other) {
        value = mmod(value - other.value, T);
    }
    void operator*=(const Res<T>& other) {
        value = mmod(value * other.value, T);
    }
    Res operator-(const Res<T>&& other) const {
        return Res(mmod(value - other.value, T));
    }
    Res operator*(const Res<T>&& other) const {
        return Res(mmod(value * other.value, T));
    }
    Res pow(ll degree) const {
        degree = degree % (T - 1);
        vector<Res<T>> deg_vals(33);
        deg_vals[0] = *this;
        ifor(1, 33) {
            deg_vals[i] = deg_vals[i - 1] * deg_vals[i - 1];
        }
        Res result = 1;
        for (int i = 0; degree > 0; ++i) {
            if (degree % 2)
                result = result * deg_vals[i];
            degree /= 2;
        }
        return result;
    }
    Res reverse() const {
        return pow(T - 2);
    }
    friend ostream& operator<<(ostream& stream, const Res& res) {
        return stream << res.value;
    }
};




#define Yes cout << "Yes\n"
#define No cout << "No\n"
#define YES cout << "YES\n"
#define NO cout << "NO\n"
#define yes cout << "yes\n"
#define no cout << "no\n"

void solve() {
    int n;
    cin >> n;
    long double v; cin >> v;
    vector<pair<long double, long double>> left, right;
    ifor(0, n) {
        long double x; cin >> x;
        long double w; cin >> w;
        if (x < 0) {
            left.push_back(mp(x, w));
        }
        else {
            right.push_back(mp(x, w));
        }
    }
    auto check = [&](long double t) {
        long double maxpos = -1000000000000, minpos = 1000000000000;
        for (auto& [p, w] : left) {
            maxpos = max(maxpos, p + w * t);
        }
        for (auto& [p, w] : right) {
            minpos = min(minpos, p - w * t);
        }
        if (minpos > maxpos) {
            return false;
        }
        return true;
    };
    long double l = 0, r = (right[0].first - left[0].first)/(right[0].second + left[0].second);
    for (int i = 0; i < 100; ++i) {
        long double m = (r + l) / 2;
        if (check(m)) {
            r = m;
        }
        else {
            l = m;
        }
    }
    cout << fixed;
    cout << setprecision(9) << r * v << "\n";
}

int main() {
    ios::sync_with_stdio(false); cin.tie(0);
    int t = 1;
    cin >> t;
    while (t--) {
        solve();
    }
    return 0;
}