#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
using namespace std;
#define trav(a, x) for(auto& a : x)
#define FOR(i, a, b) for (int i=(a); i<=(signed)(b); i++)
#define ROF(i, a, b) for (int i=(a); i>=(signed)(b); i--)
#define F0R(i, a) for (int i=0; i<(signed)(a); i++)
#define vi vector<int>
#define f first
#define s second
#define all(v) (v).begin(), (v).end()
typedef long long ll;

const ll mod = 1e9 + 7;

int main() 
{	
    ios_base::sync_with_stdio(0); cin.tie(0);
    int t; cin >> t;
    while(t--) {
        int n, v; cin >> n >> v;
        vector<pair<ll, int>> pos(n);
        F0R(_, n) {
            cin >> pos[_].first >> pos[_].second;
        }
        double lo = 0, hi = 1e12;
        F0R(_, 150) {
            double mid = (lo+hi)/2;
            double mx = -1e18, mn = 1e18;
            for(auto [p, speed] : pos) {
                if(p < 0) {
                    mx = max(p + speed*mid, mx);
                }
                else {
                    mn = min(mn, p - speed*mid);
                }
            }
            if(mx < mn) lo = mid;
            else hi = mid;
        }
        cout << setprecision(16) << v*hi << "\n";
    }
    return 0;
}