#include "bits/stdc++.h"

using namespace std;

#define mxn 1e5+5
#define fastio ios_base::sync_with_stdio(false), cin.tie(nullptr)
#define endl '\n'
typedef long long ll;
typedef long double ld;

int solve(){

    int n; ld vr; cin >> n >> vr;
    vector<pair<ld,ld>> arr(n);
    for(int i = 0; i < n; i++){
        cin >> arr[i].first >> arr[i].second;
    }

    // ld t1 = 1e13,t2 = 1e13;

    ld l = -1e13,r = 1e13;

    for(int i = 0; i < n; i++){
        if(arr[i].first < 0){
            l = max(l, arr[i].first);
        }else{
            r = min(r, arr[i].first);
        }
    }

    // cout << l <<' ' << r << endl;

    int th = 100;
    ld eps = 1e-9;
    ld ans = 0;
    while(th--){
        ld md = (l+r)/2;
        // cout << md << endl;
        // bool pass = true;
        ld tp = 1e13, tn = 1e13;
        for(int i = 0; i < n; i++){
            if(arr[i].first < 0){
                tn = min(tn, (md - arr[i].first)/ arr[i].second);
            }
            else{
                tp = min(tp, (arr[i].first - md)/ arr[i].second);
            }
        }

        if(tp > tn){
            l = md;
        }else{
            r = md;
        }
        if(th == 0) ans = tp;
    }

    cout << fixed << setprecision(9) << ans * vr << endl;

    return 0;
}

int main(){
    fastio;

    int t = 1; 
    cin >> t;

    while(t--){
        solve();
    }

    return 0;
}