#include <algorithm>
#include <iostream>
constexpr int p(1e9+7),N(310);
int f[N][N],cnt[N],g[N],t[N],ifac[N],fac[N],inv[N];
int binom(int a,int b){return 1ll*fac[a]*ifac[b]%p*ifac[a-b]%p;}
int fp(int a,int b){int ans(1),off(a);while(b){if(b&1) ans=1ll*ans*off%p;off=1ll*off*off%p;b>>=1;}return ans;}
int main()
{
	int n,k;std::ios::sync_with_stdio(false);std::cin.tie(nullptr);
	std::cin>>n>>k;for(int i(1),t;i<=n;++i) std::cin>>t,++cnt[t];
	int m(0);for(int i(1);i<=n;++i) m=std::max(m,cnt[i]);
	f[0][0]=1;
	inv[1]=1;for(int i(2);i<N;++i) inv[i]=1ll*(p-p/i)*inv[p%i]%p;
	fac[0]=ifac[0]=1;for(int i(1);i<N;++i) fac[i]=1ll*fac[i-1]*i%p,ifac[i]=1ll*ifac[i-1]*inv[i]%p;
	for(int i(1);i<=m;++i)
	{
		int cur(0);
		for(int j(2),l(1);j<=i;++j,l=1ll*l*i%p)
		{
			for(int k(1);i-k>=j-1;++k)
			{
				f[i][j]=(f[i][j]+1ll*f[i-k][j-1]*t[k]%p*binom(i-1,k-1))%p;
			}
			cur=(cur+1ll*f[i][j]*l)%p;
		}
		g[i]=(i<=k)?(i==1?1:fp(i,i-2)):0;
		g[i]=(g[i]-cur+p)%p;
		t[i]=1ll*g[i]*i%p;f[i][1]=t[i];
	}
	static int r[N];r[0]=1;
	for(int i(1),tot(0);i<=n;++i) if(cnt[i])
	{
		for(int j(tot+cnt[i]);j>=0;--j)
		{
			int cur(0);
			for(int k(0);k<=cnt[i] && k<=j;++k) cur=(cur+1ll*r[j-k]*f[cnt[i]][k])%p;
			r[j]=cur;
		}
		tot+=cnt[i];
	}
	int ans(1ll*r[1]*inv[n]%p);
	for(int i(2),j(1);i<=n;j=1ll*j*n%p,++i) ans=(ans+1ll*j*r[i])%p;
	std::cout<<ans<<std::endl;
	return 0;
}