#include <bits/stdc++.h>
#define int long long
#define T long double
const T eps = 1e-9;

using namespace std;

void solve() {
    int n, v; cin >> n >> v;
    vector<pair<int, int>> h(n);
    for(auto& [a, b] : h) {
        cin >> a >> b;
    }
    T lo = 0, hi = 1e14;
    const T oo = 1e18;
    for(int r = 0; r < 70; r++) {
        T mid = (lo + hi) / 2;
        T najd = -oo;
        T najbl = oo;
        for(int i = 0; i < n; i++) {
            if(h[i].first < 0) najd = max(najd, h[i].first + h[i].second * mid);
            else najbl = min(najbl, h[i].first - h[i].second * mid);
        }
        if(najbl < najd) {
            hi = mid;
        }
        else {
            lo = mid;
        }
    }
    cout << v * hi << '\n';
}

int32_t main() {
    cin.tie(0)->sync_with_stdio(0);
    cout << fixed << setprecision(20);
    int t; cin >> t;
    while(t--) solve();
}