#include<bits/stdc++.h>
using namespace std;
int main()
{
	ios_base::sync_with_stdio(false);
	int T;
	cin>>T;
	while(T--)
	{
		int n,V;
		cin>>n>>V;
		vector<long long> p(n+5),v(n+5);
		for(int i=1;i<=n;i++)
		{
			cin>>p[i]>>v[i];
		}
		auto check=[&](long double t)
		{
			long double maxx=-1e18,minn=1e18;
			for(int i=1;i<=n;i++)
			{
				if(p[i]>0)minn=min(minn,p[i]-v[i]*t);
				else maxx=max(maxx,p[i]+v[i]*t);
			}
//			cerr<<"check "<<t<<' '<<minn<<' '<<maxx<<endl;
			return minn<=maxx;
		};
		long double l=0,r=1e12;
		for(int tt=1;tt<=100;tt++)
		{
			double mid=(l+r)/2;
			if(check(mid))r=mid;
			else l=mid;
		}
		cout<<fixed<<setprecision(8)<<l*V<<endl;
		
	}
	
	return 0;
}