#include<iostream>
#include<cstdio>
#include<cmath>
#define N 5000
using namespace std;
int read()
{
    char c=0;
    int sum=0,f=1;
    while (c!='-'&&(c<'0'||c>'9')) c=getchar();
    if (c=='-') c=getchar(),f=-1;
    while ('0'<=c&&c<='9') sum=sum*10+c-'0',c=getchar();
    return sum*f;
}
struct reads
{
    int x,y;
};
reads st[N+1];
int T,n,m,sm;
int main()
{
    int x,y;
    long long sx,sy;
    double ans;
    T=read();
    for (int qt=1;qt<=T;++qt)
    {
	n=read(),m=read(),ans=0;
	for (int i=1;i<=n;++i) x=read(),y=read(),st[i].x=x-y,st[i].y=x+y;
	for (int i=1;i<=n;++i)
	    for (int j=1;j<=n;++j)
		for (int k=1;k<=n;++k)
		    for (int t=1;t<=n;++t)
			for (int w=0;w<=min(3,m);++w)
			{
			    sm=m-w;
			    sx=1ll*st[i].x*((sm+3)>>2)+1ll*st[j].y*((sm+2)>>2)-1ll*st[k].x*((sm+1)>>2)-1ll*st[t].y*(sm>>2);
			    sy=1ll*st[i].y*((sm+3)>>2)-1ll*st[j].x*((sm+2)>>2)-1ll*st[k].y*((sm+1)>>2)+1ll*st[t].x*(sm>>2);
			    ans=max(ans,sqrt(sx*sx+sy*sy));
			}
	printf("Case #%d: %0.10lf\n",qt,ans);
    }
    return 0;
}