#include<bits/stdc++.h>
#define inf 1e18
#define eps 1e-6
#define FOR(i,a,b) for(int i=a;i<=b;i++)
#define REP(i,a,b) for(int i=a;i>=b;i--)
#define db double
#define ve vector<int>
#define pa pair<int,int>
#define fr first
#define sd second
#define pb push_back
#define mp make_pair
#define MEM(a) memset(a,0,sizeof(a))
typedef long long ll;
typedef unsigned long long ull;
using namespace std;
inline ll read()
{
	char ch = getchar();
	ll s = 0, w = 1;
	while (ch < '0' || ch > '9') {if (ch == '-')w = -1; ch = getchar();}
	while (ch >= '0' && ch <= '9') {s = s * 10 + ch - '0'; ch = getchar();}
	return s * w;
}
#define N 400010
#define db double
#define int ll
int n; ll  V;
ll p[N], v[N];
int ck(double T)
{
	db A = 1e12, B = 1e12;
	// cout << "GG:" << T << endl;
	for (int i = 1; i <= n; i ++)
	{
		if (p[i] > 0) {A = min(A, 1.0 * p[i] - 1.0 * T * v[i]); }
		if (p[i] < 0) {B = min(B, 1.0 * (-p[i]) - 1.0 * T * v[i]);}
		// cout << "EEE:" << T * v[i] << endl;
	}
	// cout << T << " " << ((A + B) <= 0) << endl;
	// if ((A + B) > 0) {cout << "???:" << A << ' ' << B << endl;}
	return (A + B <= 0);
}
void sol()
{
	cin >> n >> V;
	for (int i = 1; i <= n; i ++)cin >> p[i] >> v[i];
	db l = 0, r = 1e12, ans = 0;
	int T = 80;
	while (T --)
	{
		db mid = (l + r) / 2.0;
		if (ck(mid))ans = mid, r = mid - eps;
		else l = mid + eps;
	}
	cout << fixed << setprecision(15) << 1.0 * ans * V << '\n';
}
signed main()
{
	//freopen(".in","r",stdin);
	//freopen(".out","w",stdout);
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	int T; cin >> T;
	while (T --)sol();
	return 0;
}