#include <bits/stdc++.h>
#define task ""
#define ll long long
using namespace std;

struct pos
{
    ll x, y;
};

const int N = 1e5 + 5;
pos p[N];
int n, k;
double res = 0;

double cross(pos x, pos y)
{
    return x.x*y.y - x.y*y.x;
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    if (fopen(task".inp", "r"))
    {
        freopen(task".inp", "r", stdin);
        freopen(task".out", "w", stdout);
    }

    int t; cin >> t;
    cout << fixed;
    while (t--)
    {
        cin >> n >> k;
        for (int i = 0; i < n; i++) cin >> p[i].x >> p[i].y;
        res = 0;
        int l = 0, r = k%n, a = -1;
        double cur = 0;
        for (int i = (l+1)%n; i != r; i = (i+1)%n) cur += cross(p[(i-1+n)%n], p[i]);
        cur += cross(p[(r-1+n)%n], p[r]);
        for (int i = (l-1+n)%n; i != r; i = (i-1+n)%n)
        {
            double area = cur + cross(p[r], p[i]) + cross(p[i], p[l]);
            if (area > res) res = area, a = i;
        }
        for (r = (r+1)%n; r != k%n; r = (r+1)%n)
        {
            cur += cross(p[(r-1+n)%n], p[r]) - cross(p[l], p[(l+1)%n]);
            l = (l+1)%n;
            if (a == r) a = (r+1)%n;
            double pre = cur + cross(p[r], p[a]) + cross(p[a], p[l]), area;
            while (a != l)
            {
                a = (a+1)%n;
                if (a == l)
                {
                    a = (l-1+n)%n;
                    break;
                }
                area = cur + cross(p[r], p[a]) + cross(p[a], p[l]);
                if (area > pre) pre = area;
                else
                {
                    a = (a-1+n)%n;
                    break;
                }
            }
            res = max(res, pre);
        }
        cout << setprecision(12) << res/2 << '\n';
    }

    return 0;
}