#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<iomanip>
#include<algorithm>
#include<vector>
#include<map>
#include<queue>
#include<bitset>
#include<set> 
#define int long long
#define lowbit(x) x&(-x)
#define mp make_pair
#define rep(i,x,n) for(int i=x;i<=n;i++)
#define per(i,n,x) for(int i=n;i>=x;i--)
#define forE(i,x) for(int i=head[x];i;i=nxt[i])
#define pii pair<int,int>
#define fi first
#define se second
using namespace std;
const int maxn=1e6+5;
const int mod=998244353;
const int INF=1e9;
inline int read()
{
	int x=0,f=1;char c=getchar();
	while(c<'0'||c>'9')
	{
		if(c=='-') f=-1;
		c=getchar();
	}
	while(c>='0'&&c<='9')
	{
		x=x*10+(c-'0');
		c=getchar();
	}
	return x*f;
}

using point_t=int;  //全局数据类型，可修改为 long long 等

constexpr point_t eps=0;
constexpr long double PI=3.1415926535897932384l;

// 点与向量
template<typename T> struct point
{
    T x,y;

    bool operator==(const point &a) const {return (abs(x-a.x)<=eps && abs(y-a.y)<=eps);}
    bool operator<(const point &a) const {if (abs(x-a.x)<=eps) return y<a.y-eps; return x<a.x-eps;}
    bool operator>(const point &a) const {return !(*this<a || *this==a);}
    point operator+(const point &a) const {return {x+a.x,y+a.y};}
    point operator-(const point &a) const {return {x-a.x,y-a.y};}
    point operator-() const {return {-x,-y};}
    point operator*(const T k) const {return {k*x,k*y};}
    point operator/(const T k) const {return {x/k,y/k};}
    T operator*(const point &a) const {return x*a.x+y*a.y;}  // 点积
    T operator^(const point &a) const {return x*a.y-y*a.x;}  // 叉积，注意优先级
    int toleft(const point &a) const {const auto t=(*this)^a; return (t>eps)-(t<-eps);}  // 向量与向量的to-left 测试 1left -1right 0on
    T len2() const {return (*this)*(*this);}  // 向量长度的平方
    T dis2(const point &a) const {return (a-(*this)).len2();}  // 两点距离的平方

    // 涉及浮点数
    long double len() const {return sqrtl(len2());}  // 向量长度
    long double dis(const point &a) const {return sqrtl(dis2(a));}  // 两点距离
    long double ang(const point &a) const {return acosl(max(-1.0l,min(1.0l,((*this)*a)/(len()*a.len()))));}  // 向量夹角
    point rot(const long double rad) const {return {x*cos(rad)-y*sin(rad),x*sin(rad)+y*cos(rad)};}  // 逆时针旋转（给定角度）
    point rot(const long double cosr,const long double sinr) const {return {x*cosr-y*sinr,x*sinr+y*cosr};}  // 逆时针旋转（给定角度的正弦与余弦）
};

using Point=point<point_t>;

// 多边形
template<typename T> struct polygon
{
    vector<point<T>> p;  // 以逆时针顺序存储
};

using Polygon=polygon<point_t>;

//凸多边形
template<typename T> struct convex: polygon<T>
{

};

using Convex=convex<point_t>;

int T;

signed main()
{
    int T=read();
    while(T--)
    {
        int n=read(),k=read();
        Convex C;
        C.p.resize(n+5);
        rep(i,1,n) C.p[i]={read(),read()}; 
        int l=1,r=k,now=0,pos=k+1;
        int ans=0;
        now+=C.p[n]^C.p[1];
        rep(i,1,k-1) now+=C.p[i]^C.p[i+1];
        for(;l<=n;l++)
        {
            
            int nxt=(r==n)?1:r+1;
            int pre=(l==1)?n:l-1;
            now-=C.p[pre]^C.p[l];
            now+=C.p[r]^C.p[nxt];
            if(pos==nxt) pos=(pos==n)?1:pos+1;
            while(1)
            {
                Point v1=C.p[l]-C.p[pos],v2=C.p[nxt]-C.p[pos];
                int nxtpos = (pos==n)?1:pos+1;
                if(nxtpos==l) break;
                Point v3=C.p[l]-C.p[nxtpos],v4=C.p[nxt]-C.p[nxtpos];
                if(abs(v3^v4)>=abs(v1^v2)) pos=nxtpos;
                else break;
            }
            Point v1=C.p[l]-C.p[pos],v2=C.p[nxt]-C.p[pos];
            ans=max(ans,abs(v1^v2)+now+(C.p[nxt]^C.p[l]));
            r=nxt;
        }
        printf("%.12Lf\n",(long double)(1.0*ans/2.0));
    }
    
}