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

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef long long lint;

const double inf = 1e18;

lint N, V;
vector<pll> l, r;

void exe() {
    cin >> N >> V;

    l.clear(); r.clear();

    for (int i=0; i<N; i++) {
        lint x, v;
        cin >> x >> v;

        if (x < 0) l.emplace_back(x, v);
        else r.emplace_back(x, v);
    }

    auto able = [&](double x) {
        double lmx = -inf, rmn = inf;

        for (auto [p, v] : l) lmx = max(lmx, p + x * v);
        for (auto [p, v] : r) rmn = min(rmn, p - x * v);

        return rmn <= lmx;
    };

    double l = 0.0, r = 1e13;

    for (int _=0; _<100; _++) {
        double m = (l+r) / 2;

        if (able(m)) r = m;
        else l = m;
    }

    cout << fixed << setprecision(10);
    cout << r * V << '\n';
}

int main()
{
    ios_base::sync_with_stdio(false); cin.tie(NULL);

    int TC;
    cin >> TC;
    // scanf("%d", &TC);
    while(TC--)
    {
        exe();
    }
}