#include <bits/stdc++.h>

#define ll long long

using namespace std;

const ll N = 1e6 + 10, MM = 1e9 + 7, MAX = 1e18;


int solve() {
	int n; cin >> n;
	ll v; cin >> v;
	vector<pair<ll, ll>>lef, rig;
	for (int i = 0; i < n; i++) {
		ll a, b; cin >> a >> b;
		if (a < 0) {
			lef.emplace_back(a, b);
		}
		else {
			rig.emplace_back(a, b);
		}
	}

	double l = 0, r = 1e18;
	double time = 0;
	int num = 100;
	while (abs(r - l) > 1e-9&&num) {
		double mid = l + (r - l) / 2.0;
		double mxlef = -MAX, mnrig = MAX;
		for (auto x : lef) {
			mxlef = max(mxlef, mid * x.second + x.first);
		}
		for (auto x : rig) {
			mnrig = min(mnrig, x.first - mid * x.second);
		}
		if (mnrig <= mxlef) {
			time = mid;
			r = mid;
		}
		else {
			l = mid;
		}
		num--;
	}
	printf("%.10f\n", time * v);
	return 0;
}

int main() {
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	int t = 1;
	cin >> t;
	int i = 1;
	while (t--) {
		//cout << "case " << i << ": ";
		solve();
	}
	return 0;
}
/*
204

*/