/***********************************************
Source Code

Problem: 1018		User: zhouzp15
Memory: 844K		Time: 110MS
Language: G++		Result: Accepted
***********************************************/

#include <iostream>
#include <iomanip>
#include <cstring>
#include <cstdio>
#define MAX 0x1f1f1f
#define N 110
using namespace std;

int MIN, kmin;
int T, n, m[N], b[N][N], p[N][N];
int f[500];
double maxbp = -1.0;
bool ok[500];

int main()
{
	cin >> T;
	while (T--)
	{
		cin >> n;
		int Max = -1, Min = MAX;
		memset (ok, 0, sizeof (ok));
		memset (f, 0, sizeof (f));
		for (int i = 1; i <= n; i++)
		{
			cin >> m[i];
			for (int j = 1; j <= m[i]; j++)
			{
				cin >> b[i][j] >> p[i][j];
				if (b[i][j] > Max) Max = b[i][j];
				if (b[i][j] < Min) Min = b[i][j];
			}
		}
		
		for (int i = 1; i <= n; i++)
		{
			for (int j = Min; j <= Max; j++)
			{
				MIN = MAX, kmin = 0;
				for (int k = 1; k <= m[i]; k++)
				{
					if (b[i][k] >= j && p[i][k] < MIN)
						kmin = k, MIN = p[i][k];
					if (b[i][k] == j)
						ok[j] = true;
				}
				if (kmin)
					f[j] += MIN;
				else 
					f[j] = MAX;
			}
		}

		maxbp = -1.0;
		for (int i = Min; i <= Max; i++)
			if ((double) i / f[i] > maxbp && ok[i]) 
				maxbp = (double)i / f[i];
				
		cout << fixed << setprecision (3) << maxbp << endl;
		
	}
	return 0;
}