import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.Comparator;

public class Solution {
    public static void main(String[] args) throws Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int q = Integer.parseInt(br.readLine());
        for (int i = 0; i < q; i++) {
            int n = Integer.parseInt(br.readLine());
            int[][] vals = new int[n][2];
            for (int j = 0; j < n; j++) {
                String[] strs = br.readLine().split(" ");
                vals[j][0] = Integer.parseInt(strs[0]);
                vals[j][1] = Integer.parseInt(strs[1]);
            }
            solve(vals);
        }
    }

    private static Comparator<int[]> COMPARATOR1 = new Comparator<int[]>() {
        @Override
        public int compare(int[] o1, int[] o2) {
            if (o1[0] == o2[0]) {
                return Integer.compare(o1[1], o2[1]);
            } else {
                return Integer.compare(o1[0], o2[0]);
            }
        }
    };

    private static Comparator<int[]> COMPARATOR2 = new Comparator<int[]>() {
        @Override
        public int compare(int[] o1, int[] o2) {
            if (o1[1] == o2[1]) {
                return Integer.compare(o1[0], o2[0]);
            } else {
                return Integer.compare(o1[1], o2[1]);
            }
        }
    };

    private static void solve(int[][] vals) {
        int[][] valsx = vals;
        int[][] valsy = vals.clone();
        Arrays.sort(valsx, COMPARATOR1);
        Arrays.sort(valsy, COMPARATOR2);
        int x1 = valsx[0][0];
        int x2 = valsx[vals.length - 1][0];
        int y1 = valsy[0][1];
        int y2 = valsy[vals.length - 1][1];

        if ((x1 == 0 && x2 == 0) || (y1 == 0 && y2 == 0)) {
            System.out.println("NO"); // degenerate
            return;
        }

        for (int[] val : vals) {
            if (val[0] != x1 && val[0] != x2 && val[1] != y1 && val[1] != y2) {
                System.out.println("NO");
                return;
            }
        }

        System.out.println("YES");
    }
}