#include <bits/stdc++.h>
using namespace std;
#define fo(i,j,k) for(int i=(j),end_i=(k);i<=end_i;i++)
#define ff(i,j,k) for(int i=(j),end_i=(k);i< end_i;i++)
#define fd(i,j,k) for(int i=(j),end_i=(k);i>=end_i;i--)
#define DEBUG(x) cerr<<#x<<"="<<x<<endl
#define all(x) (x).begin(),(x).end()
#define cle(x) memset(x,0,sizeof(x))
#define lowbit(x) ((x)&-(x))
#define VI vector<int>
#define ll long long
#define ull unsigned ll
#define lll __int128
#define db double
#define lb long db
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define endl "\n"
template<class T>inline void read(T &x) {
    x=0; char ch=getchar(); bool f=0;
    for(;ch<'0'||ch>'9';ch=getchar()) f|=(ch=='-');
    for(;ch>='0'&&ch<='9';ch=getchar()) x=x*10+(ch^48);
    if(f) x=-x;
}
template<class T,class... V>
inline void read(T &a,V&... b){read(a); read(b...);}
mt19937_64 rnd(chrono::steady_clock::now().time_since_epoch().count());
const db inf = 1e20;
void Solve() {
    int n,m;
    vector<pair<ll,ll>> a[2];
    read(n,m);
    fo(i,1,n) {
        ll p,v;
        read(p,v);
        a[p>0].push_back({p,v});
    }
    db l = 0, r = 1e15, mid;
    fo(t,1,100) {
        mid = (l + r) / 2;
        db mx = -inf;
        db mi = inf;
        for(auto [x,y]:a[0]) mx = max(mx,x+y*mid);
        for(auto [x,y]:a[1]) mi = min(mi,x-y*mid);
        if(mi <= mx) {
            r = mid;
        }
        else l = mid;
    }
    printf("%.12lf\n",l * m);
}
int main() {
    int T = 1;
    read(T);
    for(;T--;) Solve();
    return 0;
}