#include<bits/stdc++.h>

using namespace std;

#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()

using ll = long long;
using ld = double;

const int N = 4e5 + 5;
const ld eps = 1e-9;
pair<ld, ld> m[N], p[N];
int l_, r_;

bool check(ld t) {
    ld mx = -1e18;
    ld mn = 1e18;

    for (int i = 0; i < l_; i++) {
        mx = max(mx, m[i].first + t * m[i].second);
    }

    for (int i = 0; i < r_; i++) {
        mn = min(mn, p[i].first - t * p[i].second);
    }

    return mn <= mx;
}

void solve() {
    int n, v;
    cin >> n >> v;
    l_ = r_ = 0;
    for (int i = 0; i < n; i++) {
        ll x, y;
        cin >> x >> y;
        if (x < 0)
            m[l_++] = {x, y};
        else
            p[r_++] = {x, y};
    }

    long double l = 0, r = 1e14;

    for (int _ = 0; _ < 100; _++) {
        ld mid = (l + r) / 2;
        if (check(mid))
            r = mid;
        else
            l = mid;
    }
    check(r);
    cout << setprecision(20) << fixed << r * v << '\n';
}

int main() {
#ifndef LOCAL
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
#else
    freopen("input.txt", "r", stdin);
#endif
    int t;
    cin >> t;
    while (t--)
        solve();
    return 0;
}