#pragma GCC optimize(2)
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef __int128_t int128;
typedef pair<int, int> pii;
#define iofast ios::sync_with_stdio(false),cin.tie(0),cout.tie(0)
#define lowbit(x) (x&(-x))
#define inv(x) qpow(x,mod-2)
#define debug(x) cout << (#x) << " = " << x << endl
#define range(x) (x).begin(), (x).end()

const int iINF = 0x3f3f3f3f;
const ll llINF = 0x3f3f3f3f3f3f3f3f;
const ll mod = 998244353;

/*---------------------------------------*/

void solve()
{
    int n,v;
    cin>>n>>v;

    vector<pair<ll,int>>now;
    for(int i=1;i<=n;++i){
        ll x,y;
        cin>>x>>y;
        now.push_back({x,y});
    }

    long double l=0,r=1E12;

    for(int _=1;_<=100;++_){
        long double mid=(l+r)/2;
        bool flag=false;
        long double mx=-1E28,mi=1E28;

        for(const auto& [p,vv]:now){
            // cout<<vv<<'\n';
            if(p<0)
                mx=max(mx,vv*mid+p);
            else
                mi=min(mi,p-vv*mid);
        }
        // cout<<mi<<' '<<mx<<'\n';
        if(mi<mx)
            r=mid;
        else
            l=mid;
    }
    cout<<fixed<<setprecision(15)<<l*v<<'\n';

}

/*---------------------------------------*/

int main()
{
    iofast;
    int t = 1;
    cin >> t;
    while (t--)
        solve();

    return 0;
}