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

using i64 = long long;

struct Point {
    i64 x = 0, y = 0;
};

Point operator-(Point a, Point b) {
    return {a.x - b.x, a.y - b.y};
}
i64 cross(Point a, Point b) {
    return a.x * b.y - a.y * b.x;
}

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);

#ifdef LOCAL
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif

    auto solve = [&]() {
        int n, k;
        cin >> n >> k;

        vector<Point> p(n);
        for (auto &[x, y] : p) {
            cin >> x >> y;
        }

        i64 s = 0;
        for (int i = 0; i < k; i++) {
            s += cross(p[i], p[i + 1]);
        }

        i64 ans = 0;

        for (int i = 0, j = k; i < n; i++) {
            j = max(j, i + k);
            while (cross(p[(i + k) % n] - p[i], p[(j + 1) % n] - p[j % n]) > 0) {
                j++;
            }
            ans = max(ans, s + cross(p[(i + k) % n], p[j % n]) + cross(p[j % n], p[i]));
            s += cross(p[(i + k) % n], p[(i + k + 1) % n]);
            s -= cross(p[i], p[(i + 1) % n]);
        }

        cout << ans / 2 << '.' << ans % 2 * 5 << '\n';
    };
    
    int t;
    cin >> t;

    while (t--) {
        solve();
    }
    
    return 0;
}