#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <climits>

int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */
    int q;    //!< number of queries
    std::cin >> q;
    
    for (int i = 0; i < q; ++i)
    {
        int n;    //!< number of points
        std::cin >> n;
        
        int x_min = INT_MIN;
        int x_max = INT_MAX;
        int y_min = INT_MIN;
        int y_max = INT_MAX;
        
        bool al_rect = true;
        
        for (int j = 0; j < n; ++j)
        {
            int x, y;
            std::cin >> x >> y;
            
            if ((x != x_min) && (x != x_max))
            {        
                if (INT_MIN == x_min)
                    x_min = x;
                else if (INT_MAX == x_max)
                {
                    x_max = x;
                }
                else
                {
                    al_rect = false;
                    break;
                }
            }
            
            if ((y != y_min) && (y != y_max))
            {        
                if (INT_MIN == y_min)
                    y_min = y;
                else if (INT_MAX == y_max)
                {
                    y_max = y;
                }
                else
                {
                    al_rect = false;
                    break;
                }
            }         
        }
        
        if (true == al_rect)
            std::cout << "YES" << std::endl;
        else
            std::cout << "NO" << std::endl;
    }
    
    
    return 0;
}