#include <bits/stdc++.h>
#pragma GCC optimize("O3")
#pragma GCC target("avx")
#define ll long long
#define INF 1000000005
#define MOD 1000000007
#define EPS 1e-10
#define rep(i,n) for(int i=0;i<(int)(n);++i)
#define rrep(i,n) for(int i=(int)(n)-1;i>=0;--i)
#define srep(i,s,t) for(int i=(int)(s);i<(int)(t);++i)
#define each(a,b) for(auto& (a): (b))
#define all(v) (v).begin(),(v).end()
#define len(v) (int)(v).size()
#define zip(v) sort(all(v)),v.erase(unique(all(v)),v.end())
#define cmx(x,y) x=max(x,y)
#define cmn(x,y) x=min(x,y)
#define fi first
#define se second
#define pb push_back
#define show(x) cout<<#x<<" = "<<(x)<<endl
#define spair(p) cout<<#p<<": "<<p.fi<<" "<<p.se<<endl
#define sar(a,n) cout<<#a<<":";rep(pachico,n)cout<<" "<<a[pachico];cout<<endl
#define svec(v) cout<<#v<<":";rep(pachico,v.size())cout<<" "<<v[pachico];cout<<endl
#define svecp(v) cout<<#v<<":";each(pachico,v)cout<<" {"<<pachico.first<<":"<<pachico.second<<"}";cout<<endl
#define sset(s) cout<<#s<<":";each(pachico,s)cout<<" "<<pachico;cout<<endl
#define smap(m) cout<<#m<<":";each(pachico,m)cout<<" {"<<pachico.first<<":"<<pachico.second<<"}";cout<<endl

using namespace std;

typedef pair<int,int> P;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<double> vd;
typedef vector<P> vp;
typedef vector<string> vs;

const int MAX_N = 200000;

#define getchar getchar_unlocked

inline int in() {
    int n = 0; short c;
    while ((c = getchar()) >= '0') n = n * 10 + c - '0';
    return n;
}

int inv[MAX_N],fac[MAX_N],finv[MAX_N];

void make()
{
	fac[0] = fac[1] = 1;
	finv[0] = finv[1] = 1;
	inv[1] = 1;
	for(int i=2;i<MAX_N;i++){
		inv[i] = MOD - (ll)inv[MOD%i] * (MOD/i) % MOD;
		fac[i] = (ll)fac[i-1] * i % MOD;
		finv[i] = (ll)finv[i-1] * inv[i] % MOD;
	}
}

inline int prod(int a, int b)
{
	return (a < b) ? 0 : ((ll)fac[a] * finv[a-b] % MOD);
}

void extgcd(int a,int b, int& x,int& y)
{
	if(b){
		extgcd(b, a%b, y, x);
		y -= (a/b)*x;
	}else{
		x = 1, y = 0;
	}
}

int mod_inverse(int a, int m)
{
	int x, y;
	extgcd(a,m,x,y);
	return (m + x % m) % m;
}

int cnt[MAX_N];

int main()
{
    int n = in(), B = in();
    rep(i,n){
        cnt[in()]++;
    }
    make();
    int id = 0, ad = 0, ans = B, s = 0, t = 0, pl = B;
    bool flag = false;
    rrep(i,MAX_N){
        if(!cnt[i]) continue;
        s = (ll)prod(id+cnt[i]-1, cnt[i]-1) * cnt[i] % MOD;
        t = ((ll)s * B + prod(id+cnt[i]-1, cnt[i])) % MOD;
        if(t){
            ad = (ad + (ll)s * mod_inverse(t, MOD) % MOD) % MOD;
            pl = (ll)pl * t % MOD;
        }else{
            if(!flag){
                flag = true;
                pl = (ll)pl * s % MOD;
            }else{
                pl = 0;
            }
        }
        ans = (ll)ans * t % MOD;
        id += cnt[i];
    }
    cout << ((ll)ans * ad  + (flag ? pl : 0)) % MOD << "\n";
    return 0;
}