#ifdef MY_LOCAL
#include "D://competitive_programming/debug/debug.h"
#define debug(x) cerr << "[" << #x<< "]:"<<x<<"\n"
#else
#define debug(x) 
#endif
#define REP(i, n) for(int i = 0; i < (n); i ++)
#define REPL(i,m, n) for(int i = (m); i < (n); i ++)
#define SORT(arr) sort(arr.begin(), arr.end())
#define LSOne(S) ((S)&-(S))
#define sz(X) ((int)X.size())
#define READ(arr) for(auto &a: arr){cin>>a;}
#define SUM(arr) accumulate((arr).begin(), (arr).end(), 0LL)
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;
typedef long long ll;
#define int ll
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int, int> ii;
typedef vector<ii> vii;
typedef vector<vii> vvii;
typedef tree<int,null_type,less<int>, rb_tree_tag, tree_order_statistics_node_update> ost;
const ll INF = 1e18;
#define double long double
void solve() {
	int n,v;cin>>n>>v;
	vii arr1;
	vii arr2;
	REP(i, n) {
		int p,vv;cin>>p>>vv;
		if (p < 0) {
			arr1.push_back({-p, vv});
		} else {
			arr2.push_back({p, vv});
		}
	}
	double EPS = 1e-9;
	double mn = 0;
	double mx = 1e13;
	while (mx - mn > EPS*mn) {
		double md = (mx + mn)/2;
		double b1 = -INF;
		double b2 = -INF;
		for (auto [x,y]: arr1) {
			b1 = max(b1, y*md - x);
		}
		for (auto [x,y]: arr2) {
			b2 = max(b2, y*md - x);
		}
		if (b1 + b2 >= 0) {
			mx = md;
		} else {
			mn = md;
		}
	}
	cout<<setprecision(13)<<mn*v<<"\n";
}

signed main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(NULL); 
	int tc;
	cin>>tc;
	REP(i, tc) {
		solve();
	}

}