#include <bits/stdc++.h>
using namespace std;
#define rep(i, x, y) for (int i = x; i <= y; ++i)
#define per(i, x, y) for (int i = x; i >= y; --i)
#define ll long long
#define pb push_back
#define pii pair<int, int>
#define pil pair<int, ll>
#define all(x, y) x.begin() + y, x.end()
inline ll read()
{
    ll x = 0, f = 1; char ch = getchar();
    while (!isdigit(ch)) {if (ch == '-') f = -1; ch = getchar();}
    while (isdigit(ch)) {x = x * 10 + ch - 48; ch = getchar();}
    return x * f;
}

void solve()
{
    int n = read(), k = read();
    vector<int> x(n), y(n);
    rep(i, 0, n - 1) x[i] = read(), y[i] = read();
    double s = 0;
    deque<int> q;
    auto cal = [&](int u, int v)
    {
        return 1ll * x[u] * y[v] - 1ll * x[v] * y[u];
    };
    if (n == 3)
    {
        double ans = abs(cal(0, 1) + cal(1, 2) + cal(2, 0)) / 2.0;
        printf("%.1lf", ans);
        return;
    }
    auto add = [&](int i)
    {
        // cout << "add " << i << '\n'; 
        if (q.empty() || q.size() == 1) q.push_back(i);
        else
        {
            int l = q.front(), r = q.back();
            s += abs(cal(l, r) + cal(r, i) + cal(i, l)) / 2.0;
            q.push_back(i);
        }
    };
    auto del = [&]()
    {
        // cout << "del " << q.front() << '\n'; 
        if (q.size() <= 2) q.pop_front();
        else
        {
            int lst = q.front();
            q.pop_front();
            int l = q.front(), r = q.back();
            s -= abs(cal(lst, l) + cal(l, r) + cal(r, lst)) / 2.0;
        }
    };
    rep(i, 0, k - 1) add(i);
    int now = k - 1;
    double ans = 0;
    rep(i, 0, n - 1)
    {
        now = (now + 1) % n;
        add(now);
        int l = 0, r = n - k;
        auto get = [&](int add) -> double
        {
            int x = (q.back() + add) % n;
            ll ret = cal(q.front(), q.back()) + cal(q.back(), x) + cal(x, q.front());
            return abs(ret) / 2.0;
        };
        double t = 0;
        while (l + 1 < r)
        {
            int mid = l + r >> 1;
            double a1 = get(mid - 1), a2 = get(mid + 1);
            if (a1 < a2) t = max(t, a2), l = mid;
            else t = max(t, a1), r = mid;
        }
        // printf("%d %.1lf %.1lf\n", i, s, t);
        t = max({t, get(l), get(r)});
        ans = max(ans, s + t);
        del();
    }
    printf("%.1lf", ans);
}

int main()
{
    int t = read();
    while (t--)
    {
        solve();
        if (t) putchar('\n');
    }
}