#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

#define openr() freopen("input.txt","r",stdin)
#define openw() freopen("output.txt","w",stdout)
#define mp make_pair
#define fi first
#define se second
#define int long long int


using namespace std;
using namespace __gnu_pbds;
template <typename T>
using ordered_set=tree<T,null_type,less<T>,rb_tree_tag,tree_order_statistics_node_update>;

const long double inf=1e18;
const int mod= 1000000007;


void show()
{
    long double n,v;    cin>>n>>v;
    vector<pair<long double,long double>>a(n);
    for(int i=0;i<n;i++)
    {
        cin>>a[i].fi>>a[i].se;
    }
    sort(a.begin(), a.end());
    long double r= 1e12;
    long double l=0;
    long double res= 0;
    long double thres_hold= 0.000000001;
    int cnt=10000;
    while(l + thres_hold < r && cnt-- ){

        long double temp= l+r;
        long double mid= (l+r)/2.0;
        long double ls=-inf;
        long double rs= inf;
        for(int i=0;i<n;i++)
        {
            // fi pos
            // se vel
            long double dis= a[i].se * mid;
            if(a[i].fi < 0) ls= max(ls, a[i].fi + dis);
            else rs= min(rs, a[i].fi - dis);
        }
        if(ls <= rs )
        {
            // tang time
            res= max(res, mid);
            l= mid+thres_hold;
        }
        else    {
            r= mid - thres_hold;
        }
    }
    cout<<fixed<<setprecision(10)<<res*v;
}

int32_t main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    //openr();
    int tc; cin>>tc;
    while(tc--)
    {
        show();
        cout<<"\n";
    }
    return 0;
}