#ifndef NYCU_MyGO
#define NYCU_MyGO
#include NYCU_MyGO __FILE__ NYCU_MyGO

const double INF = 1e13;

void solve() {
    int N; cin >> N;
    double V; cin >> V;
    
    vector<pii> cops_l, cops_r;
    for (int i = 0; i < N; ++i) {
        int p, v; cin >> p >> v;
        if (p < 0) cops_l.eb(-p, v);
        if (p > 0) cops_r.eb( p, v);
    }
    sort(ALL(cops_l)), sort(ALL(cops_r));
    
    double ans = 0.0;
    double lo = -cops_l[0].first, hi = cops_r[0].first, mi;
    for (int _round = 1; _round <= 50; ++_round) {
        mi = (lo + hi) / 2.0;
        
        double min_time_l = INF, min_time_r = INF;
        for (auto [p, v] : cops_l) chmin(min_time_l, (p + mi) / v);
        for (auto [p, v] : cops_r) chmin(min_time_r, (p - mi) / v);
        ans = V * min_time_l;
        
        if (min_time_l > min_time_r) hi = mi;
        else                         lo = mi;
    }
    cout << fixed << setprecision(15) << ans << "\n";
}

int32_t main() {
    fastIO();
    
    int t = 1; cin >> t;
    for (int _ = 1; _ <= t; ++_) {
        solve();
    }
    
    return 0;
}

#else

#ifdef local
#define _GLIBCXX_DEBUG 1
#endif
#pragma GCC optimize("Ofast", "unroll-loops")
#include <bits/stdc++.h>
using namespace std;

using i64 = long long;
#define int i64
using f80 = long double;
#define dobule f80
using pii = pair<int, int>;
template <typename T> using Prior = std::priority_queue<T>;
template <typename T> using prior = std::priority_queue<T, vector<T>, greater<T>>;

#define eb emplace_back
#define ef emplace_front
#define ee emplace
#define pb pop_back
#define pf pop_front
#define ALL(x) begin(x), end(x)
#define RALL(x) rbegin(x), rend(x)
#define SZ(x) ((int)(x).size())

#ifdef local
#define fastIO() void()
#define debug(...) \
    fprintf(stderr, "\u001b[33m"), \
    fprintf(stderr, "At [%s], line %d: (%s) = ", __FUNCTION__, __LINE__, #__VA_ARGS__), \
    _do(__VA_ARGS__), \
    fprintf(stderr, "\u001b[0m")
template <typename T> void _do(T &&_t) { cerr << _t << "\n"; }
template <typename T, typename ...U> void _do(T &&_t, U &&..._u) { cerr << _t << ", ", _do(_u...); }
#else
#define fastIO() ios_base::sync_with_stdio(0), cin.tie(0)
#define debug(...) void()
#endif

template <typename T, typename U> bool chmin(T &lhs, U rhs) { return lhs > rhs ? lhs = rhs, 1 : 0; }
template <typename T, typename U> bool chmax(T &lhs, U rhs) { return lhs < rhs ? lhs = rhs, 1 : 0; }

#endif

/*
                                                                                                                
                                                                                                                
                                                                                                                
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iiiii                                iiii  iiii    iiiiiiiiiiii                             ii                  
 iii                              iiii   iiii       iiiiiiii                                                    
                               iiiii   iiii                                                                     
                             iiii     iiii                                                                      
                           iiii    iiiii                                                                        
                         iii     iiiii                                                                          
                       iii     iiiii                                                                            
                      iii   iiiiii                                                                              
                      iiiiiiiii                                                                                 
                      iiiiii                                                                                    
                                                                                                                
                                                                                                                
                                                                                                                
*/