#include <bits/stdc++.h>
using namespace std;
using i64 = long long;

void solve() {
    int n, w;
    cin >> n >> w;
    vector<pair<i64, i64>> a, b;
    for (int i = 0; i < n; i++) {
        i64 p, v;
        cin >> p >> v;
        if (p < 0) {
            a.emplace_back(p, v);
        } else {
            b.emplace_back(p, v);
        }
    }
    sort(a.begin(), a.end(), greater());
    sort(b.begin(), b.end());

    double lo = 0, hi = 3e12;
    for (int i = 0; i < 70; i++) {
        double mid = (lo + hi) / 2;

        double l = -1e18, r = 1e18;
        for (auto [p, v] : a) {
            l = max(l, mid * v + p);
        }
        for (auto [p, v] : b) {
            r = min(r, -mid * v + p);
        }

        if (l < r) {
            lo = mid;
        } else {
            hi = mid;
        }
    }

    double ans = lo * w;
    cout << ans << '\n';
}

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

    cout << setprecision(15) << fixed;

    int T;
    cin >> T;

    while (T--) {
        solve();
    }

    // double a = 2999999999999.999511718750000, b = 3000000000000;
    // double t = abs(a - b) / max(1.0, b);
    // cerr << t << '\n';

    return 0;
}