#include<stdio.h>
#include<string.h>
#include<algorithm>
#include<assert.h>
using namespace std;
int T,n,k,A[31],C[31],mul[302];
double fact[40],total[32][302];
double solve(int x,int y)
{
	memset(mul,0,sizeof(mul));
	int c = max(A[x]-k,0) + max(A[y]-k,0),ck=A[x]+1,sk=A[x]+A[y];
	int rem;
	for(int i=0;i<=k-1;i++){
		mul[i] = 0;
		for(int j=1;j<=A[x];j++)
			if( j + k >= ck+i && j+k <= sk+i )	mul[i]++;
	}
	double answer=0,cases;
	memset(total,0,sizeof(total));
	total[0][0]=1;
	for(int i=1;i<=n;i++){
		if( i==x || i==y)	continue;
		for(int l=n-3;l>=0;l--){
			for(int j=k-1;j>=0;j--){
				if(j+A[i]>=k)	continue;
				total[l+1][j+A[i]] += total[l][j];
			}
		}
	}
	for(int i=0;i<=n-2;i++){
		rem = n-i-2;
		for(int j=0;j<=k-1;j++){
			answer = answer + (double)(rem+1)*fact[rem]*fact[i]*(double)total[i][j]*(double)mul[j];
		}
	}
	return answer ;
}
int main()
{	
	double answer;
	fact[0]=1;
	for(int i=1;i<=30;i++)	fact[i]=fact[i-1]*i;
	scanf("%d",&T);
	while(T--){
		answer=0;
		scanf("%d%d",&n,&k);
		assert(n<=20);
		assert(k<=200 && k>=1);
		for(int i=1;i<=n;i++){
			scanf("%d%d",&A[i],&C[i]);
			assert(A[i]<=10 && A[i]>=1);
			assert(C[i]<=n && C[i]>=1);
		}
		for(int i=1;i<=n;i++){
			for(int j=1;j<=n;j++){
				if(i==j)	continue;
				if(C[i] != C[j])	continue;
				answer+=solve(i,j);
			}
		}
		for(int i=1;i<=n;i++){
			answer = answer + max(A[i]-k,0)*(double)n*fact[n-1];
		}
		printf("%lf\n",answer/fact[n]);
	}
	return 0;
}