#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int mod = 1e9 + 9;
int n, K;
struct point {
	ll x, y;
} a[200005];
ll Dot(point x, point y) { return x.x * y.x + x.y * y.y; }
ll Cross(point x, point y) { return x.x * y.y - x.y * y.x; }
ll Dis(point x, point y) { return (x.x - y.x) * (x.x - y.x) + (x.y - y.y) * (x.y - y.y); }
point operator+(point x, point y) { return {x.x + y.x, x.y + y.y}; }
point operator-(point x, point y) { return {x.x - y.x, x.y - y.y}; }
ll Calc(point a, point b, point c) { return Cross(b - a, c - a); }
ll Get(ll x, ll y, ll l, ll r) {
	while (r - l > 1) {
		int m1 = (l + r) / 2, m2 = m1 + 1;
		if (Calc(a[x], a[y], a[m1]) > Calc(a[x], a[y], a[m2])) r = m1;
		else l = m2;
	}
	ll ans = 0;
	for (int i = l; i <= r; i++) ans = max(ans, Calc(a[x], a[y], a[i]));
	return ans;
}
void Solve() {
	scanf("%d%d", &n, &K);
	for (int i = 0; i < n; i++) {
		scanf("%lld%lld", &a[i].x, &a[i].y);
		a[i + n] = a[i];
	}
	// 0~K
	ll cursum = 0, ans = 0;
	for (int i = 0; i + 1 < K; i++) {
		cursum += Cross(a[K] - a[i + 1], a[i] - a[i + 1]);
	}
	for (int i = 0; i < n; i++) {
		ans = max(ans, cursum + Get(i, i + K, i + K + 1, i + n - 1));
		cursum -= Cross(a[i + K] - a[i + 1], a[i] - a[i + 1]);
		cursum += Cross(a[i + K + 1] - a[i + K], a[i + 1] - a[i + K]);
	}
	printf("%.1Lf\n", 1.0l * ans / 2);
}
int main() {
	int t;
	scanf("%d", &t);
	while (t--) Solve();
}