#include <bits/stdc++.h>
//G
using namespace std;
double mint, calc;
vector <double> polvn (400001);
vector <double> polpn (400001);
vector <double> polvp (400001);
vector <double> polpp (400001);

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);
    long long int z, n, nn, np, v, pi, vi;
    cin >> z;
    while (z--){
        mint = 100000000000000;
        np = 0;
        nn = 0;
        cin >> n >> v;
        while (n--){
            cin >> pi >> vi;
            if (pi < 0){
                polpn[nn] = pi;
                polvn[nn] = vi;
                nn ++;
            } else{
                polpp[np] = pi;
                polvp[np] = vi;
                np ++;
            }
        } for (int i = 0; i < nn; i++){
            for (int j = 0; j < np; j++){
                calc = (polpp[j] - polpn[i])/(polvp[j] + polvn[i]);
                mint = min(mint, calc);
            }
        }
        cout << fixed << setprecision(8); 
        cout << mint*v << "\n";

    } return 0;
}