#include "bits/extc++.h"

using namespace std;

template <typename T>
void dbgh(const T& t) {
    cerr << t << endl;
}

template <typename T, typename... U>
void dbgh(const T& t, const U&... u) {
    cerr << t << " | ";
    dbgh(u...);
}

#ifdef DEBUG
#define dbg(...)                                           \
    cerr << "L" << __LINE__ << " [" << #__VA_ARGS__ << "]" \
         << ": ";                                          \
    dbgh(__VA_ARGS__)
#else
#define cerr   \
    if (false) \
    cerr
#define dbg(...)
#endif

using ld = long double;

#define endl "\n"
#define long int64_t
#define sz(x) int(std::size(x))

void solve() {
    int n;
    long vr;
    cin >> n >> vr;
    long arr[n][2];
    for (auto& [p, v] : arr) {
        cin >> p >> v;
    }
    auto check = [&](ld x) -> bool {
        ld mx = -1e100, mn = 1e100;
        for (auto& [p, v] : arr) {
            if (p < 0) {
                mx = max(mx, p + v * x);
            } else {
                mn = min(mn, p - v * x);
            }
        }
        dbg(mn, mx);
        return mn <= mx;
    };
    ld l = 0, r = 1e18;
    for (int i = 0; i < 200; i++) {
        ld mid = (l + r) / 2;
        if (check(mid)) {
            r = mid;
        } else {
            l = mid;
        }
    }
    dbg(l, r);
    cout << l * vr << endl;
}

int main() {
    cin.tie(nullptr);
    cin.exceptions(ios::failbit);
    ios_base::sync_with_stdio(false);
    cout << fixed << setprecision(8);
    int tcs;
    cin >> tcs;
    while (tcs--) {
        solve();
    }
}