#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef long double ld;
#define TIME (clock() * 1.0 / CLOCKS_PER_SEC)

// _________ vect (2D) ______________
template <typename T>
struct vect {
    T x = 0;
    T y = 0;

    vect() = default;
    vect(T x_, T y_) : x(x_), y(y_) {}

    inline T len2() const {
        return x * x + y * y;
    }

    inline ld len() const {
        return sqrtl(len2());
    }

    inline vect rotate() const {
        return vect(-y, x);
    }
};

template <typename T>
inline istream& operator>>(istream& in, vect<T>& v) {
    return in >> v.x >> v.y;
}

template <typename T>
inline ostream& operator<<(ostream& out, const vect<T>& v) {
    return out << "[" << v.x << "," << v.y << "]";
}

template <typename T>
inline vect<T> operator+(const vect<T>& a, const vect<T>& b) {
    return vect(a.x + b.x, a.y + b.y);
}

template <typename T>
inline vect<T> operator-(const vect<T>& a, const vect<T>& b) {
    return vect(a.x - b.x, a.y - b.y);
}

template <typename T>
inline vect<T> operator*(const vect<T>& a, T k) {
    return vect(a.x * k, a.y * k);
}

template <typename T>
inline T operator*(const vect<T>& a, const vect<T>& b) {
    return a.x * b.x + a.y * b.y;
}

template <typename T>
inline T operator^(const vect<T>& a, const vect<T>& b) {
    return a.x * b.y - a.y * b.x;
}

void solve() {
    int n, k;
    cin >> n >> k;
    vector<vect<ll>> v(n);
    for (int i = 0; i < n; i++) {
        cin >> v[i];
    }
    vector<ll> pref(2 * n + 1, 0);
    for (int i = 0; i < 2 * n; i++) {
        pref[i + 1] = pref[i] + (v[i % n] ^ (v[(i + 1) % n]));
    }
    auto calc_area = [&](int l, int r) {
        if (l <= r) {
            return pref[r] - pref[l] + (v[r] ^ v[l]);
        }
        return pref[r + n] - pref[l] + (v[r] ^ v[l]);
    };
    ll ans = 0;
    int st = k;
    for (int i = 0; i < n; i++) {
        int j = (i + k) % n;
        while (((v[(st + 1) % n] - v[st]) ^ (v[j] - v[i])) <= 0) {
            st = (st + 1) % n;
        }
        ans = max(ans, pref[n] - calc_area(st, i) - calc_area(j, st));
        //cerr << i + 1 << " " << j + 1 << " " << st + 1 << "\n";
    }
    cout << (ans / 2);
    if (ans % 2 == 1) {
        cout << ".5";
    }
    cout << "\n";
}

int main() {
#ifdef ONPC
    freopen("input", "r", stdin);
#endif
    ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    int t = 1;
    cin >> t;
    while (t--) {
        solve();
    }

    return 0;
}