#include <bits/stdc++.h>

using namespace std;

const int N = 100'000 + 10;
int n, k;

template<class T>
struct Point { 
  T x, y;

  Point& operator -= (const auto& rhs) { x -= rhs.x; y -= rhs.y; return *this; }
  T cross(Point rhs) { return x * rhs.y - rhs.x * y; }
  friend istream& operator >> (istream& is, auto& rhs) { 
    return is >> rhs.x >> rhs.y;
  }
  friend ostream& operator << (ostream& os, const auto& rhs) { 
    return os << "(" << rhs.x << ", " << rhs.y << ")"; 
  }
};

using point = Point<long long>;
point p[N];

int32_t main() { 
  cin.tie(0)->sync_with_stdio(0);

  int test; cin >> test;
  while (test--) { 
    cin >> n >> k;
    for (int i = 1; i <= n; ++i) cin >> p[i];
    
    // point origin = p[1];
    // for (int i = 1; i <= n; ++i) p[i] -= origin;
    // for (int i = 1; i <= n; ++i) cerr << p[i] << "\n";

    k += 1;

    long long answer = 0, botArea = 0;
    deque<int> q(k); iota(q.begin(), q.end(), 1);
    for (int i = 1; i < k; ++i) botArea += p[i].cross(p[i % n + 1]);
    auto area = [&](int top) { return botArea + p[q.back()].cross(p[top]) + p[top].cross(p[q.front()]); };

    auto fwd = [&](int pos) { return pos == n ? 1 : pos + 1; };
    int top = fwd(k);
    
    answer = area(top);
    auto shiftLeft = [&]() { 
      if (top == q.back()) top = fwd(top);
      while (fwd(top) != q.front() && area(fwd(top)) >= area(top)) top = fwd(top);
      answer = max(answer, area(top));
    };

    shiftLeft();
    for (int i = 2; i <= n; ++i) { 
      botArea -= p[q[0]].cross(p[q[1]]);              q.pop_front();
      botArea += p[q.back()].cross(p[fwd(q.back())]); q.push_back(fwd(q.back()));
      shiftLeft();
    }
    
    
    cout << answer / 2;
    if (answer & 1) cout << ".5";
    cout << "\n";
  }
}