#include<iostream>
#include<algorithm>
#include<cmath>
#include<stdio.h>
#include<cstring>
#define re register
#define int long long
using namespace std;
inline int read()
{
	int x=0,f=1;
	char c=getchar();

	while(c<'0'||c>'9')
	{
		if(c=='-') f=-1;
		c=getchar();
	}

	while('0'<=c&&c<='9')
	{
		x=(x<<3)+(x<<1)+(c^48);
		c=getchar();
	}
	return x*f;
}

const int maxn = 100005;
int n,k;

struct Point
{
	int x,y;
}po[maxn];

int cross(Point p,Point q)
{ 
	return p.x*q.y-p.y*q.x;
}

double S(Point p,Point q,Point r)
{
	Point v1;
	Point v2;
	v1.x = q.x-p.x; v1.y = q.y-p.y;
	v2.x = r.x-p.x; v2.y = r.y-p.y;
	return 0.5*fabs( cross(v1,v2) );
}

signed main()
{
	int T=read();
	while(T--)
	{
		n=read(); k=read(); 
		for(int i=0;i<n;++i) po[i].x=read(),po[i].y=read();
		int area = 0;
		for(int i=1;i<=k;++i) area += cross(po[i-1],po[i]);
		double ans = 0.0;
		int cur = k+1;
		for(int b=0;b<n;++b)
		{
			int c = (b+k)%n;
			if(b!=0)
			{
				area -= cross(po[b-1],po[b]);
				area += cross( po[(c-1+n)%n], po[c%n] );
			}
			int now = fabs( area + cross(po[c],po[b]) );
			if(k==1) now = 0;
			while( S( po[b],po[c],po[cur] ) <= S( po[b],po[c],po[(cur+1)%n] ) && (cur+1)%n !=b ) 
				cur = (cur+1)%n;
			ans = max( ans,  0.5*now + S( po[b],po[c],po[cur] ) );
		}
		printf("%.1lf\n",ans);
	}
	return 0;
}