#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>
#include <stdio.h>
#include <string.h>
#include <array>
#include <atomic>
#include <chrono>
#include <condition_variable>
#include <forward_list>
#include <future>
#include <initializer_list>
#include <mutex>
#include <random>
#include <ratio>
#include <regex>
#include <scoped_allocator>
#include <system_error>
#include <thread>
#include <tuple>
#include <typeindex>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
#include <cassert>
using namespace std;
void __print(int x) {cerr << x;}
void __print(long x) {cerr << x;}
void __print(long long x) {cerr << x;}
void __print(unsigned x) {cerr << x;}
void __print(unsigned long x) {cerr << x;}
void __print(unsigned long long x) {cerr << x;}
void __print(float x) {cerr << x;}
void __print(double x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << '\'' << x << '\'';}
void __print(const char *x) {cerr << '\"' << x << '\"';}
void __print(const string &x) {cerr << '\"' << x << '\"';}
void __print(bool x) {cerr << (x ? "true" : "false");}
template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ','; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? "," : ""), __print(i); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
#ifndef ONLINE_JUDGE
#define debug(x...) cerr << "[" << #x << "] = ["; _print(x)
#else
#define debug(x...)
#endif

// #define int long long
#define fi first
#define se second
#define all(x) x.begin(), x.end()
#define pb push_back
#define BOOST ios_base::sync_with_stdio(false),cin.tie(NULL),cout.tie(NULL);
typedef long long ll;
typedef long double ld;
typedef pair<int,int> ii;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ii> vii;
typedef vector<ll> vll;
void test_case() {
    int n;
    ll vr;
    cin >> n >> vr;
    vector<pair<ll,ll>> left, right;
    for(int i = 0; i < n; i++) {
        ll x, v;
        cin >> x >> v;
        if(x < 0) left.pb({x, v});
        else right.pb({x, v});
    }
    auto check = [&](ld x) {
        ld left_max = -1e13, right_min = 1e13;
        for(auto p : left) {
            left_max = max(left_max, p.first + p.second * x);
        }
        for(auto p : right) {
            right_min = min(right_min, p.first - p.second * x);
        }
        return left_max > right_min;
    };
    ld l = 0, r = 1e12 + 5;
    for(int i = 0; i < 200; i++) {
        ld mid = (l + r) / 2;
        if(check(mid)) {
            r = mid;
        } else {
            l = mid;
        }
    }
    cout << fixed << setprecision(12) << vr * l << "\n";
}
int32_t main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    int tc = 1;
    cin >> tc;
    while(tc--) {
        test_case();
    }
    return 0;
}