#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
#define double long double

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;
}

inline int mod_pow(int a, int n, int mod){
    int ret = 1;
	while(n){
		if(n & 1) ret = (ll)ret * a % mod;
		a = (ll)a * a % mod;
		n >>= 1;
	}
	return ret;
}

const double PI = acos(-1);

complex<double> operator* (const complex<double> a, const complex<double> b){
    return complex<double>(a.real()*b.real()-a.imag()*b.imag(),a.real()*b.imag()+a.imag()*b.real());
}

vector<complex<double> > fft(vector<complex<double> > a,bool rev = false)
{
    int n = a.size(),h = 0;
    for(int i = 0; 1 << i < n; i++) h++;
    //バタフライ演算前の係数の並び替え
    rep(i,n){
        int j = 0;
        rep(k,h){
            j |= (i >> k & 1) << (h-1-k);
        }
        if (i < j) swap(a[i], a[j]);
    }
    //バタフライ演算
    for(int i = 1; i < n; i *= 2) {
        rep(j,i){
            complex<double> w = polar((double)1.0, 2*PI/(i*2)*(rev?-1:1)*j);
            for(int k = 0; k < n; k += i * 2) {
                complex<double> s = a[j+k];
                complex<double> t = a[j+k+i]*w;
                a[j+k] = s+t;
                a[j+k+i] = s-t;
            }
        }
    }
    if (rev) rep(i,n) a[i] /= n;
    return a;
}

void mul(vector<int>& a, vector<int>& b, vector<int>& c)
{
    int s = (int)a.size() + (int)b.size() - 1,t = 1;
    while (t < s) t *= 2;
    vector<complex<double> > A(t), B(t);
    c.resize(t);
    rep(i,a.size()) A[i].real(a[i]);
    rep(i,b.size()) B[i].real(b[i]);
    A = fft(A),B = fft(B);
    rep(i,t) A[i] *= B[i];
    A = fft(A, true);
    c.resize(s);
    //整数に直す
    rep(i,s) c[i] = round(A[i].real());
}

vector<int> c[2*MAX_N];
int cnt[MAX_N];

int main()
{
    int n = in(), B = in();
    rep(i,n){
        cnt[in()]++;
    }
    make();
    int id = 0, num = 0;
    priority_queue<P, vector<P>, greater<P> > que;
    rrep(i,MAX_N){
        if(!cnt[i]) continue;
        c[num] = {prod(id+cnt[i]-1, cnt[i]) % MOD, (int)((ll)prod(id+cnt[i]-1, cnt[i]-1) * cnt[i] % MOD)};
        que.push(P(2, num++));
        id += cnt[i];
    }
    while(len(que) >= 2){
        int p = que.top().se; que.pop();
        int q = que.top().se; que.pop();
        mul(c[p], c[q], c[num]);
        que.push(P(len(c[num]), num));
        num++;
    }
    int index = que.top().se;
    int ans = 0, nB = 1;
    rep(i, len(c[index])){
        ans = (ans + (((ll)c[index][i] * i) % MOD) * nB) % MOD;
        nB = (ll)nB * B % MOD;
    }
    cout << ans << "\n";
    return 0;
}