#include <bits/stdc++.h>
#define N 304
#define mod 1000000007
using namespace std;
typedef long long ll;

int n, K, cnt[N], c[N];
ll C[N][N], g[N], f[N][N];

ll pw (ll bs, ll t)
{
    ll res=1;
    while (t) {
        if (t&1) { res=res*bs%mod; }
        bs=bs*bs%mod; t>>=1;
    }
    return res;
}

int main ()
{
    // freopen("0test.in", "r", stdin);
    // freopen("0test.out", "w", stdout);

    scanf("%d %d", &n, &K);
    for (int i=1; i<=n; i++) { scanf("%d", &c[i]); cnt[c[i]]++; }

    for (int i=0; i<=n; i++) {
        C[i][0]=1;
        for (int j=1; j<=i; j++) { C[i][j]=(C[i-1][j]+C[i-1][j-1]) %mod;}
    }

    f[1][1]=1; g[1]=1;
    for (int k=2; k<=n; k++) {
        g[k]=(k>K ? 0 : pw(k, k-2));
        for (int i=2; i<=k; i++) {
            for (int j=1; j<k; j++) {
                f[k][i]+=f[k-j][i-1]*C[k-1][j-1] %mod *g[j] %mod;
                f[k][i]%=mod;
            }
            g[k]-=f[k][i]*pw(k, i-2)%mod; f[k][1]%=mod;
        }
        f[k][1]=g[k]*k%mod; g[k]=g[k]*k%mod;
    }

    ll ans=1;
    for (int i=1; i<=n; i++) if (cnt[i]) {
        ll res=0;
        for (int k=1; k<=cnt[i]; k++) {
            res+=f[cnt[i]][k]*pw(n, k) %mod;
        }
        res%=mod;
        ans=ans*res%mod;
    }
    ans=ans*pw((ll)n*n%mod, mod-2)%mod;
    ans=(ans+mod)%mod;
    printf("%lld\n", ans);

    return 0;
}