#include <bits/stdc++.h>
using namespace std;
using ui = unsigned int;
using ull = unsigned long long;
using ll = long long;
#define endl '\n'
using pii = pair<int, int>;
using pll = pair<ll, ll>;
const int maxn = 2e5 + 10;
const int mod = 1000000007;
#define inl inline
#define fr(i, a, b) for (int i = a; i <= b; i++)
#define ford(i, a, b) for (int i = a; i >= b; i--)
#define forall(i, a) for (auto &i : a)

/**
   ____         ___ _____
  / ___| _   _ / _ \___ /
  \___ \| | | | | | ||_ \
   ___) | |_| | |_| |__) |
  |____/ \__, |\___/____/
         |___/
*/
istream &operator>>(istream &in, vector<int> &v)
{
    for (auto &i : v)
        in >> i;
    return in;
}
ostream &operator<<(ostream &out, vector<int> &v)
{
    for (auto &i : v)
        out << i << " ";
    return out;
}
bool _output = 1;

void solve()
{
    int n, vt;
    cin >> n >> vt;

    vector<int> v(n);
    vector<int> a(n);

    for (int i = 0; i < n; i++)
    {
        cin >> a[i] >> v[i];
    }
#define db long double
    const db EPS = 1e-8;
    db l = 0, r = 1e14;
    int cnt = 0;
    while (l + EPS < r)
    {
        ++cnt;
        db mid = (l + r) / 2;
        auto check = [&](db x)
        {
            db mx = LLONG_MIN, mn = LLONG_MAX;
            for (int i = 0; i < n; i++)
            {
                if (a[i] > 0)
                    mn = min(mn, a[i] - x * v[i]);
                else
                    mx = max(mx, a[i] + x * v[i]);
            }
            return mn >= EPS + mx;
        };
        if (check(mid))
            l = mid;
        else
            r = mid;
    }
    cout << fixed << setprecision(10) << l * vt << endl;
}
signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int _ = 1;
    if (_output)
        cin >> _;
    while (_--)
        solve();
    return 0;
}