#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef unsigned long long int ull;

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
ll myRand(ll B) {
    return (ull)rng() % B;
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int q; cin >> q;
    while (q--){
        int n; cin >> n;
        ll V; cin >> V;
        vector<ll> p(n),v(n);
        for (int i = 0; i < n; ++i) {
            cin >> p[i] >> v[i];
        }
        double l = 0, r = 1e12;
        for (int i = 0; i < 100; ++i) {
            double mid = (l+r)/2.0;
            double mx = -1e18;
            double mi = 1e18;
            for (int j = 0; j < n; ++j) {
                if(p[j] > 0){
                    mi = min(mi, -mid*v[j]+p[j]);
                }
                else{
                    mx = max(mx, mid*v[j]+p[j]);
                }
                if(mi <= mx){
                    break;
                }
            }
            if(mi <= mx){
                r = mid;
            }
            else{
                l = mid;
            }
        }
        printf("%.9f\n", r*V);
    }
}