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

#define bug(x) cerr << #x << " = " << x << '\n';
typedef pair<double, double> pld;

bool check(vector<pld> L, vector<pld> R, double t) {
    double mn = 1e12;
    double mx = -1e12;
    for (auto x: L) {
        mx = max(mx, x.first + t * x.second);
    }
    for (auto x: R) {
        mn = min(mn, x.first - t * x.second);
    }
    if (mn <= mx)
        return true;
    return false;
}

void solve() {
    int n;
    double v;
    cin >> n >> v;
    vector<pld> p(n);
    vector<pld> L, R;
    for (auto &x: p) {
        cin >> x.first >> x.second;
        if (x.first < 0) {
            L.push_back(x);
        } else {
            R.push_back(x);
        }
    }
    double l = 0, r = 1e12;//(R[0].first - L[0].first) / (R[0].second + L[0].second);
    for (int i= 0; i < 100; i++) {
        double mid = (l + r) / 2.;
        if (check(L, R, mid)) {
            r = mid;
        } else {
            l = mid;
        }
    }
    cout << r * v << '\n';
}

int main() {
    ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
    cout << setprecision(8) << fixed;
    int Q;
    cin >> Q;
    while (Q--) {
        solve();       
    }
    return 0;
}