#include <bits/stdc++.h>
// #include <bits/extc++.h>
// using namespace __gnu_cxx;
// using namespace __gnu_pbds;
using i64 = long long;
using namespace std;
const int N = 4e5 + 5;
// const int B = 500;
// const int M = 50005;
// const int base = 17131;
const int mod = 998244353;
// const int mod = 1e9 + 7;
// const double pi = acos(-1);

int n, v0;
i64 pos[N], v[N];
bool check(double time)
{
    double l = -1e18, r = 1e18;
    for (int i = 1; i <= n; i++)
    {
        if (pos[i] < 0)
            l = max(l, time * v[i] + pos[i]);
        else
            r = min(r, 1.0 * pos[i] - time * v[i]);
    }
    if (l >= r)
        return true;
    else
        return false;
}
void solve()
{
    cin >> n >> v0;
    for (int i = 1; i <= n; i++)
        cin >> pos[i] >> v[i];
    double l = 0, r = 1e12, mid;
    int cnt = 100;
    while (cnt--)
    {
        mid = (l + r) / 2.0;
        if (check(mid))
            r = mid;
        else
            l = mid;
    }
    cout << r * v0 << '\n';
}
signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int t = 1;
    cin >> t;
    cout << fixed << setprecision(12);
    while (t--)
        solve();
}