#include <bits/stdc++.h>
#define N 400011
#define ll long long
#define lll __int128
#define dubble long double
#define pii pair<ll,ll>
#define s1 first
#define s2 second
using namespace std;
int t,n,v,n1,n2,nb;
pii a[N],a1[N],a2[N],b[N];
dubble slope(pii a,pii b){return (dubble)(b.s2-a.s2)/(b.s1-a.s1);}
int main()
{
	scanf("%d",&t);while(t--)
	{
		scanf("%d%d",&n,&v);
		for(int i=1;i<=n;++i)
		{
			scanf("%lld%lld",&a[i].s2,&a[i].s1);
			if(a[i].s2<0)a[i].s1=-a[i].s1;
		}
		n1=n2=0;
		for(int i=1;i<=n;++i)
		{
			if(a[i].s1<0)a1[++n1]=a[i];
			else a2[++n2]=a[i];
		}
		sort(a1+1,a1+1+n1);sort(a2+1,a2+1+n2);
		nb=0;
		for(int i=1;i<=n2;++i)
		{
			while(nb>=2&&(lll)(a2[i].s2-b[nb].s2)*(b[nb].s1-b[nb-1].s1)<=(lll)(b[nb].s2-b[nb-1].s2)*(a2[i].s1-b[nb].s1))--nb;
			b[++nb]=a2[i];
		}
		dubble ans=1e30;
		for(int i=1;i<=n1;++i)
		{
			int L=1,R=nb;
			while(L<=R)
			{
				int M=L+R>>1;
				ans=min(ans,slope(a1[i],b[M]));
				if(M==R||slope(a1[i],b[M])<slope(a1[i],b[M+1]))R=M-1;else L=M+1;
			}
		}
		printf("%.20Lf\n",ans*v);
	}return 0;
}