//I wrote this code 4 u today
#include <bits/stdc++.h>

template<class t> using vc = std::vector<t>;

#define nd node*
#define pnd pair<nd, nd>

typedef long long ll;

template<const ll MOD>
struct mod_mul : std::multiplies<const ll> {
    ll operator()(const ll a, const ll b) {
        return (a * b) % MOD;
    }
};


template<typename T>
inline void sort(T &a) {
    std::sort(a.begin(), a.end());
}

template<typename T>
inline void unique(T &a) {
    a.resize(std::unique(a.begin(), a.end()) - a.begin());
}

template<typename T>
inline void reverse(T &a) {
    std::reverse(a.begin(), a.end());
}

const ll INF = 9023372036854775808ll;
const ll MOD = 1000000007ll;

typedef long double ld;

int main() {
    std::cin.tie(nullptr)->ios_base::sync_with_stdio(false);
    std::cout << std::fixed << std::setprecision(18);
    int z;
    std::cin >> z;
    while (z--) {
        ll n, v;
        std::cin >> n >> v;
        vc<std::pair<ll, ll>> p(n);
        for (auto &i : p) std::cin >> i.first >> i.second;
        ld l = 0, r = 16e16 + 5;
        for (int i = 0; i < 120; ++i) {
            ld mid = (l + r) / 2.0;
            ld mn = 1e9 + 5, mx = -1e9 - 5;
            for (auto [p, v] : p) if (p > 0) mn = std::min(mn, p - v * mid);
            for (auto [p, v] : p) if (p < 0) mx = std::max(mx, p + v * mid);
            if (mn <= mx) r = mid;
            else l = mid;
        }
        std::cout << r * v << '\n';
    }
}