#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>
#include <cmath>
#include <bitset>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <algorithm>
#include <complex>
#include <unordered_map>
#include <unordered_set>
#include <random>
#include <cassert>
#include <fstream>
#define popcount __builtin_popcount
using namespace std;
typedef long long int ll;
typedef pair<int, int> P;
const ll MOD=1e9+7;
ll powmod(ll a, ll k){
    ll ap=a, ans=1;
    while(k){
        if(k&1){
            ans*=ap;
            ans%=MOD;
        }
        ap=ap*ap;
        ap%=MOD;
        k>>=1;
    }
    return ans;
}
ll inv(ll a){
	return powmod(a, MOD-2);
}
ll f[1500001], invf[1500001];
void fac(int n){
    f[0]=1;
    for(ll i=1; i<=n; i++) f[i]=f[i-1]*i%MOD;
    invf[n]=inv(f[n]);
    for(ll i=n-1; i>=0; i--) invf[i]=invf[i+1]*(i+1)%MOD;
}
ll comb(int x, int y){
    if(x<y) return 0;
    return f[x]*invf[y]%MOD*invf[x-y]%MOD;
}
int n;
ll B;
int c[200010];
ll a[200010], b[200010];
int main()
{
    cin>>n>>B;
    for(int i=0; i<n; i++){
        int s; cin>>s;
        c[s]++;
    }
    int s=0;
    fac(n);
    for(int i=n-1; i>=0; i--){
      if(c[i]==0){
        a[i]=0, b[i]=1;
        continue;
      }
        ll x=f[s+c[i]]*invf[s]%MOD;
        if(s==0) b[i]=0;
        else b[i]=f[s+c[i]-1]*invf[s-1]%MOD;
        a[i]=(x-b[i]+MOD)%MOD;
        s+=c[i];
    }
    ll p=B;
    ll d[200020];
    ll p1[200020], p2[200020];
    for(int i=0; i<n; i++){
        d[i]=a[i]*B+b[i];
        d[i]%=MOD;
    }
    p1[0]=1;
    for(int i=0; i<n; i++){
        p1[i+1]=p1[i]*d[i]%MOD;
    }
    p2[n]=1;
    for(int i=n-1; i>=0; i--){
        p2[i]=p2[i+1]*d[i]%MOD;
    }
    ll ans=0;
    for(int i=0; i<n; i++){
        ans+=p1[i]*p2[i+1]%MOD*a[i]%MOD;
        ans%=MOD;
    }
    cout<<ans*B%MOD<<endl;
    return 0;
}