> 真是没谁了
//============================================================================
// Name        : main1018.cpp
// Author      : 
// Version     :
// Copyright   : Your copyright notice
// Description : Hello World in C++, Ansi-style
//============================================================================

#include <iostream>
#include <vector>
#include <cstdlib>
#include <stdio.h>
using namespace std;


int mini(int a, int b){
	if(a < b) return a;
	return b;
}

class bw_pr{
	public:
		int bw;
		int pr;

	bw_pr(int b, int p): bw(b), pr(p){

	}

	bw_pr(): bw(0), pr(0){

	}
};


int partion(bw_pr* array, int p, int r) {
		bw_pr x = array[r];
		int i = p - 1;//注意这点，把i设成负值，然后作为移动的标志
		int j;
		for (j = p; j < r; j++) {
			if (array[j].bw > x.bw) {
				i++;
				bw_pr temp = array[j];
				array[j] = array[i];
				array[i] = temp;
			}
		}
		bw_pr temp = array[j];
		array[j] = array[i + 1];
		array[i + 1] = temp;
		return i+1;//返回的应该是交换后的哨兵的位置
}
		//递归解决每个划分后的小
void quickSort(bw_pr* array, int p, int r) {
		if (p < r) {
			int q = partion(array, p, r);
			quickSort(array, p, q - 1);
			quickSort(array, q + 1, r);
		}
}

int main() {
	//cout << "!!!Hello World!!!" << endl; // prints !!!Hello World!!!

	int testcase;
	cin >> testcase;
	for(int ii = 0; ii < testcase; ii++){

		int device;
		cin >> device;
		vector<bw_pr> info[100];
		for(int jj = 0; jj < device; jj++){
			int manu;
			cin >> manu;
			bw_pr temp[100];
			for(int i = 0; i < manu; i++){
				int bw, pr;
				cin >> bw >> pr;
				//bw_pr* temp_ = new bw_pr(bw, pr);
				temp[i].bw = bw;
				temp[i].pr = pr;
			}
			quickSort(temp, 0, manu-1);
			int pr = 2147483647;
			for(int i = 0; i < manu; i++){
				if(temp[i].pr < pr){
					pr = temp[i].pr;
					info[jj].push_back(temp[i]);
				}
			}
			//for(int i = 0; i < info[jj].size(); i++) cout << info[jj][i].bw << " " <<
					//info[jj][i].pr << endl;
			//delete [] temp;
		}

		vector<bw_pr> res[2];
		res[0].push_back(bw_pr(2147483647, 0));
		for(int i = 0; i < device; i++){
			vector<bw_pr>& from = res[i%2], &to = res[(i+1)%2], &ref = info[i];
			to.clear();
			//下面合并from和ref中的内容并放入to中
			int fromSize = from.size(), refSize = ref.size();
			int fromIndex = 0, refIndex = 0;
			int targetBw = mini(from[fromIndex].bw, ref[refIndex].bw);

			while(1){
				//cout << targetBw << endl;
				//找到最后一个大于等于targetBw的
				if(from[fromIndex].bw > targetBw){
					while(1){
						fromIndex++;
						if(fromIndex == fromSize || from[fromIndex].bw < targetBw) break;
					}
					fromIndex--;
				}
				if(ref[refIndex].bw > targetBw){
					while(1){
						refIndex++;
						if(refIndex == refSize || ref[refIndex].bw < targetBw) break;
					}
					refIndex--;
				}
				to.push_back(bw_pr(targetBw, from[fromIndex].pr + ref[refIndex].pr));
				//将结果放入目标中
				if(fromIndex < fromSize - 1) fromIndex++;
				if(refIndex < refSize - 1) refIndex++;
				int newtargetBw = mini(from[fromIndex].bw, ref[refIndex].bw);
				if(newtargetBw == targetBw) break;
				targetBw = newtargetBw;
			}
		}
		vector<bw_pr>& po = res[device%2];
		//for(int i = 0; i < po.size(); i++) cout << po[i].bw << " " <<
							//po[i].pr << endl;
		double b_p = 0;
		int size = po.size();
		for(int i = 0; i < size; i++){
			double newb_p = po[i].bw * 1.0 / po[i].pr;
			if(newb_p > b_p) b_p = newb_p;
		}
		printf("%.3f\n", b_p);

	}


	return 0;
}