#include<bits/stdc++.h>
#define fo(i,l,r) for(int i=l;i<=r;++i)
#define fd(i,r,l) for(int i=r;i>=l;--i)
#define ll long long
#define I inline int
#define V inline void
#define B inline bool
#define L inline ll
#define pi pair<int,int>
#define mk make_pair
#define fi first
#define se second
#define pb push_back
#define vi vector<int>
#define vii vector<pi>
using namespace std;
const int N=305,mod=1e9+7;
char St;
I read() {
	int x=0,y=1;char c=getchar();
	while(c<48||c>57) {if(c==45)y=-y;c=getchar();}
	while(c>=48&&c<=57) x=(x<<1)+(x<<3)+(c^48),c=getchar();
	return x*y;
}
int n,k,s[N];
ll pw[N],f[N][N],g[N][N],ans(1),C[N][N],inv[N];
L ksm(ll x,int y=mod-2) {
	ll t=1;for(;y;y>>=1,x=x*x%mod)if(y&1)t=t*x%mod;return t;
}
V add(ll &x,ll y) {
	(x+=y)%=mod;
}
char Ed;
int main() {
	cerr<<"memory:"<<(&St-&Ed)/1024.0<<endl;
	n=read();k=read();
	fo(i,1,n) s[read()]++;
	C[0][0]=1;
	fo(i,1,n) {
		inv[i]=ksm(i);
		C[i][0]=1;
		fo(j,1,i) C[i][j]=(C[i-1][j]+C[i-1][j-1])%mod;
	}
	fo(i,1,n) {
		pw[i]=1;
		fo(j,1,i-2) pw[i]=pw[i]*i%mod;
	}
	f[0][0]=mod-1;
	fo(i,1,n) fo(j,1,min(i,k)) fo(l,1,i) add(f[i][l],mod-1ll*C[i][j]*f[i-j][l-1]%mod*pw[j]%mod*inv[l]%mod*j%mod);
	fo(i,1,n) {
		fo(j,1,i) add(f[i][0],f[i][j]*ksm(i,j-2+mod-1)%mod);
	}
	fo(i,1,n) {
		if(!s[i]) continue;
		memset(g,0,sizeof(g));
		g[0][0]=1;
		fo(j,1,s[i]) fo(k,1,j) fo(l,1,j) add(g[j][l],g[j-k][l-1]*k%mod*C[j][k]%mod*f[k][0]%mod*n%mod*inv[l]%mod);
		ll sum=0;
		fo(j,1,s[i]) {
			add(sum,g[s[i]][j]);
		}
		ans=ans*sum%mod;
	}
	printf("%lld\n",ans*ksm(n*n,mod-2)%mod);
	cerr<<"time:"<<clock()<<endl;
	return 0;
}