#include<bits/stdc++.h>
using namespace std;
#define ll long long int
const int sz = 1e5 + 5, mod = 1e9 + 7;
int32_t main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    int t = 1; cin >> t;
    while(t--) {
        int n, v; cin >> n >> v;
        std::vector<pair<ll,int>> pos, neg;
        for(int i = 0; i < n; i++) {
            ll a; int b; cin >> a >> b;
            if(a < 0) neg.push_back({a, b});
            else pos.push_back({a, b});
        }
        double ans = 0.0;
        double lo = 0.0, hi = 1e12;
        for(int itr = 0; itr < 100; itr++) {
            double mi = (lo + hi) / 2;
            double l = -1e12, r = 1e12;
            for(auto &[a, b]:neg) l = max(l, a + b * mi);
            for(auto &[a, b]:pos) r = min(r, a - b * mi);
            if(l <= r) {
                ans = mi;
                lo = mi;
            } else hi = mi;
        }
        cout << fixed << setprecision(10) << ans * v << "\n"; 
    }
    return 0; 
}