#include <bits/stdc++.h>
#define f first
#define s second
using namespace std;
int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	int zz; cin>>zz;
	while (zz--)
	{
		long long n, v; cin>>n>>v;
		vector<pair<long long, long long>>c(n);
		for (auto &i : c) cin>>i.f>>i.s;
		long double ans=0, d=1ll<<42;
		for (int i=100; i>=0; i--, d/=2.)
		{
			ans+=d;
			long double mx=-1e12, mn=1e12;
			for (auto j : c)
			{
				if (j.f < 0)
				{
					mx=max(mx, j.f+ans*j.s);
				}
				else
				{
					mn=min(mn, j.f-ans*j.s);
				}
			}
			if (mn<mx) ans-=d;
		}
		cout<<fixed<<setprecision(10)<<ans*v<<"\n";
	}
}