#include<bits/stdc++.h>
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
#define pii pair<ll,ll>
#define rep(i,a,b) for(ll i=(a);i<=(b);++i)
#define per(i,a,b) for(ll i=(a);i>=(b);--i)
using namespace std;
bool Mbe;
ll read(){
    ll x=0,f=1;char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
    return x*f;
}
void write(ll x){
    if(x<0)putchar('-'),x=-x;
    if(x>9)write(x/10);
    putchar(x%10+'0');
}
const ll N=1e6+9;
ll T,n,V,t1,t2;
pii p[N],q[N];
bool chk(ld mid){
    ld mn1=1e18,mn2=1e18;
    rep(i,1,t1)mn1=min(mn1,p[i].first-mid*p[i].second);
    rep(i,1,t2)mn2=min(mn2,q[i].first-mid*q[i].second);
    return mn1+mn2<=0;
}
void solve(){
    n=read(),V=read();
    t1=t2=0;
    rep(i,1,n){
        ll x=read(),y=read();
        if(x<0)p[++t1]={-x,y};
        else q[++t2]={x,y};
    }
    ld l=0,r=2e12;
    rep(T,1,100){
        ld mid=(l+r)/2;
        if(chk(mid))r=mid;
        else l=mid;
    }
    cout<<fixed<<setprecision(12)<<l*V<<"\n";
}
bool Med;
int main(){
    cerr<<fabs(&Med-&Mbe)/1048576.0<<"MB\n";
    T=read();
    while(T--)solve();
    return 0;
}