#include<bits/stdc++.h>
using namespace std;
const int N=510,P=1e9+7;
int k,n,c[N];
int F[N][N],G[N],H[N],tmp[N],inv[N],pw[N][N];
int main()
{
	inv[1]=1;for(int i=2;i<N;++i)inv[i]=P-1ll*P/i*inv[P%i]%P; 
	cin>>n>>k;
	for(int i=1,x;i<=n;++i)cin>>x,++c[x];
	for(int i=0;i<N;++i){pw[i][0]=1;for(int j=1;j<N;++j)pw[i][j]=1ll*pw[i][j-1]*i%P;}
	for(int i=1;i<=n;++i)
	{
		H[i]=1;
		for(int j=1;j<=i-2;++j)H[i]=1ll*H[i]*i%P;
	}
	F[0][0]=1;
	for(int i=1;i<=n;++i)
		for(int j=1;j<=n;++j)
			for(int z=1,c=1;z<=k&&z<=i;++z)
				c=1ll*c*inv[z]%P,
				F[i][j]=(F[i][j]+1ll*c*F[i-z][j-1]%P*H[z]%P*z)%P;
	for(int i=1,d=1;i<=n;++i,d=1ll*d*i%P)
		for(int j=1,c=d;j<=n;++j)
		{
			c=1ll*c*inv[j]%P;
			F[i][j]=1ll*F[i][j]*c%P;
//			cerr<<"F: "<<i<<" "<<j<<" : "<<F[i][j]<<endl;
		}
	long long K=1ll*inv[n]*inv[n]%P,A=0;
	for(int _=1;_<=n;++_)
	{
		memset(G,0,sizeof G);G[0]=1;
		long long C=1ll*inv[n]*inv[n]%P;
		for(int i=1,s=0;i<=n;++i)if(c[i])
		{
			C=C*n%P;
			memset(tmp,0,sizeof tmp);
			for(int j=0;j<=s;++j)
				for(int t=1;t<=c[i]&&j+t<=_;++t)
					tmp[j+t]=(tmp[j+t]+1ll*F[c[i]][t]*G[j]%P*pw[n-c[i]][t-1])%P;
			memcpy(G,tmp,sizeof G);s+=c[i];
		}
//		cerr<<G[_]<<endl;
		A=(A+C*G[_])%P;
	}
//	for(int i=1;i<=n;++i)
//	{
//		K=K*n%P;(A+=K*G[i])%=P;
//	}
	cout<<A<<endl;
}