#include <bits/stdc++.h>
using namespace std;

struct hash_pairii {
  int64_t operator()(const pair<int, int> &pr) const {
    return (int64_t)(pr.first) << 32 | pr.second;
  }
};

void solve() {
  vector<pair<int, int>> v;
  unordered_multiset<pair<int, int>, hash_pairii> st;
  int n;
  cin >> n;
  for (int64_t i = 0; i < n << 1; ++i) {
    int64_t x, y;
    cin >> x >> y;
    st.emplace(x, y);
    v.emplace_back(x, y);
  }
  if ([&]() {
        for (const auto &pr : v)
          if (st.count(pr) & 1)
            return false;
        return true;
      }()) {
    cout << "1\n0 0\n";
  }
  set<pair<int64_t, int64_t>> ans;
  auto check = [&](int64_t x, int64_t y) -> bool {
    for (const auto &[a, b] : v) {
      if (!st.count({a + x, b + y}) && !st.count({a - x, b - y}))
        return false;
    }
    return true;
  };
  for (size_t i = 1; i < v.size(); ++i) {
    int64_t x = v[i].first - v[0].first;
    int64_t y = v[i].second - v[0].second;
    if (x || y && check(x, y)) {
      ans.emplace(x, y), ans.emplace(-x, -y);
    }
  }
  cout << ans.size() << '\n';
  for (const auto &[a, b] : ans)
    cout << a << ' ' << b << '\n';
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int t;
  cin >> t;
  while (t--)
    solve();
  return 0;
}