#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define X first
#define Y second
#define SZ(a) ((int)a.size())
#define pb push_back
#define ALL(v) v.begin(), v.end()

const double INF = 1e12;

void solve() {
    int n;
    ll v0;
    cin >> n >> v0;
    vector<pll> vec(n);
    for (auto &[p, v] : vec)
        cin >> p >> v;

    auto check = [&](double mid) {
        double mi = INF, mx = -INF;
        for (auto [p, v] : vec) {
            if (p < 0) mx = max(mx, v * mid + p);
            else mi = min(mi, p - v * mid);
        }
        return mx >= mi;
    };

    double l = 0, r = 1e12;
    for (int t = 0; t < 100; ++t) {
        double mid = (l + r) / 2;
        if (check(mid)) r = mid;
        else l = mid;
    }
    cout << fixed << setprecision(15) << r * v0 << "\n";
}

int main() {
    ios::sync_with_stdio(0), cin.tie(0);
    int t;
    cin >> t;
    while (t--) {
        solve();
    }
}