#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
 
using namespace std;
using namespace __gnu_pbds;
typedef long long int lld;
typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> ordered_set;
#define rep(i,a,b) for(int i=a;i<b;i++)
#define trav(a,v) for(auto a:v)
#define all(x) begin(x),end(x)

void solve(){
    int n;
    long double v;
    cin>>n>>v;
    vector<array<long double,2>> a(n);
    for(auto&[i,j]:a)cin>>i>>j;

    int iters=200;
    long double L=0;
    long double R=1e12;
    while(iters--){
	long double mid=(L+R)/2;

	bool leftDefined=false;
	bool rightDefined=false;
	long double posLeft;
	long double posRight;
	for(auto[x,y]:a){
	    if(x<0){
		if(!leftDefined){
		    leftDefined=true;
		    posLeft=x+mid*y;
		}
		else posLeft=max(posLeft,x+mid*y);
	    }
	    else{
		if(!rightDefined){
		    rightDefined=true;
		    posRight=x-mid*y;
		}
		else posRight=min(posRight,x-mid*y);
	    }
	}

	if(posLeft>posRight)R=mid;
	else L=mid;
    }

    cout<<fixed<<(v*L)<<"\n";
}

int main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	int tt=1;
	cin>>tt;
	while(tt--){
		solve();
	}
}