#include<bits/stdc++.h>
using namespace std;

long double eps = 1e-18;

int main(){
	ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	cout<<fixed<<setprecision(20);
	int t;
	cin>>t;
	while(t--){
		vector<pair<long long, long long > > cleft, cright;
		long long v;
		long long n;
		cin>>n>>v;
		for(int i=0;i<n;i++){
			long long x,y;
			cin>>x>>y;
			if(x < 0){
				cleft.push_back({x, y});
			}else{
				cright.push_back({x, y});
			}
		}
		long double l=eps, r=1e12+eps;
		long double ans = l;
		for(int kh=0;kh<300;kh++){
			long double mid = (r+l)/2.0;
			long double mxl = -1e12, mnr = 1e12;
			for(int i=0;i<(int)cleft.size();i++){
				mxl = max(mxl, mid * cleft[i].second + cleft[i].first);
			}
			for(int i=0;i<(int)cright.size();i++){
				mnr = min(mnr, -mid * cright[i].second + cright[i].first);
			}
			if(mxl >= mnr){
				r = mid - eps;
			}else{
				ans = max(ans, mid);
				l = mid + eps;
			}
		}
		cout<<ans*v<<'\n';
	}
	
	return 0;
}