#include <iostream>
#include <map>
#include <set>
#include <vector>
int main() {
    int T;
    std::cin >> T;
    while (--T >= 0) {
        int N;
        std::cin >> N;
        std::map<int, std::vector<int>> m; 
        for (int i = 0; i < N; i++) {
            int x, y;
            std::cin >> x >> y;
            m[x].push_back(y);
        }
        std::set<int> skip;
        auto v0 = m.begin()->second;
        auto v1 = m.rbegin()->second;
        skip.insert(m.begin()->first);
        skip.insert(m.rbegin()->first);
        std::set<int> pt;
        for (auto i : v0) pt.insert(i);
        for (auto i : v1) pt.insert(i);
        std::set<int> valid;
        valid.insert(*(pt.begin()));
        valid.insert(*(pt.rbegin()));
        bool bad = false;
        for (auto const &kv : m) {
            if (skip.find(kv.first) == skip.end()) {
                for (auto i : kv.second) {
                    if (valid.find(i) == valid.end()) {
                        bad = true;
                    }
                }
            }
        }
        std::cout << (bad ? "NO" : "YES") << std::endl;
    }
}