#include <bits/stdc++.h>
using namespace std;
// #define int long long
typedef long long db;
const int maxn=200005;
inline int read() {
    int r=0,f=1;
    char ch=getchar();
    while(!isdigit(ch)) {
        if(ch=='-') f=-1;
        ch=getchar();
    }
    while(isdigit(ch)) {
        r=(r<<1)+(r<<3)+(ch^48);
        ch=getchar();
    }
    return r*f;
}
struct nod{
    db x,y;    
}a[maxn];
int n,k;
int T;
inline nod operator - (nod x,nod y) {return {x.x-y.x,x.y-y.y};}
inline db cross(nod x,nod y) {return x.x*y.y-x.y*y.x;}
inline db mian(nod x,nod y) {return fabs(cross(x,y));}
inline db calc(nod a,nod b,nod c) {return mian(a-b,a-c);}

signed main()
{
    T=read();
    while(T--) {
        n=read(); k=read();
        for(int i=1;i<=n;++i) {
            int x=read(),y=read();
            a[i+n]=a[i]={x,y};
        }
        db sum=0,ans=0,now=0;
        for(int i=1;i<k;++i)
            sum+=calc(a[i],a[i+1],a[k+1]);
        int j=k+2;
        for(int i=1;i<=n;++i) {
            while(j<i+k+1) ++j;
            while(j<=n+i-1) {
                now=calc(a[i],a[k+i],a[j]);
                if(j==n+i-1) break;
                if(calc(a[i],a[k+i],a[j+1])<=now) break;
                ++j;
            }
            // cout<<i<<" "<<j<<" "<<sum<<" "<<now<<endl;
            ans=max(ans,sum+now);
            sum=sum-calc(a[i],a[i+1],a[k+i])+calc(a[i+1],a[k+i],a[k+i+1]);
        }
        printf("%.10lf\n",ans*0.5);
    }
    return 0;
}
/*

2
3 1
0 0
-1 0
0 -1
3 1
0 0
1 0
0 1


1
4 2
0 0
0 1
1 0
1 1

1
5 2
0 0
1 0
2 0
3 0
1 1

1
8 3
1 2
3 1
5 1
7 3
8 6
5 8
3 7
1 5

1
7 2
3 6
1 1
3 1
7 1
8 1
5 6
4 6

*/