//Man always remember love because of romance only!
#include<bits/stdc++.h>
using namespace std;
#define int long long
const int mod=1e9+7; 
inline int read(){
    int n=0,w=0; char ch=0;
    while(!isdigit(ch)) {w|=ch=='-';ch=getchar();}
    while(isdigit(ch)) n=(n<<3)+(n<<1)+(ch^48),ch=getchar();
    return w?-n:n;
}
inline void write(int x){
	if(x<0) putchar('-'),x=-x;
    if(x>9) write(x/10);
    putchar(x%10+'0');
}
int qpow(int x,int y){
	int res=1;
	while(y){
		if(y&1) res=res*x%mod;
		x=x*x%mod;
		y>>=1;
	}
	return res;
}
int c[301];
int fac[301],inv[301],w[301];
int f[310],g[310];
signed main(){
	int n=read(),m=read();
	for(int i=1;i<=n;i++) c[read()]++; 
	fac[0]=1,inv[0]=1;
	for(int i=1;i<=n;i++){
		fac[i]=fac[i-1]*i%mod;
		inv[i]=qpow(fac[i],mod-2); 
	}
	for(int i=1;i<=m;i++) w[i]=qpow(i,i-1)*inv[i]%mod;
	int ans=1;
	for(int i=1;i<=n;i++){
		if(c[i]){
			for(int j=1;j<=c[i];j++) f[j]=(j<=m)?(n-c[i])*w[j]%mod:0;
			g[0]=1;
			for(int j=1;j<=c[i];j++){
				g[j]=0;
				for(int k=0;k<j;k++) g[j]=(g[j]+g[k]*f[j-k]%mod*(j-k)%mod)%mod;
				g[j]=g[j]*inv[j]%mod*fac[j-1]%mod;
			}
			int res=0;
			for(int j=1;j<=c[i];j++) res=(res+j*w[j]%mod*n%mod*g[c[i]-j]%mod)%mod;
			ans=ans*res%mod*fac[c[i]-1]%mod;
		}
	}
	ans=ans*qpow(n,(mod-2)*2)%mod;
	write(ans);
	return 0;
}