#include<bits/stdc++.h>
#define int long long
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
using namespace std;
template<typename T>istream&operator>>(istream&I,vector<T>&v){for(auto&i:v)I>>i;return I;}
template<typename T>ostream&operator<<(ostream&O,vector<T>&v){for(auto&i:v)O<<i<<' ';return O;}
namespace AC{
const int mod=1e9+7;
struct matrix{
	vector<vector<int>>m;
	matrix(int N,int M):m(N,vector<int>(M,0)){}
	vector<int>&operator[](int x){return m[x];}
	matrix operator*(matrix&a){
		matrix res(m.size(),a.m[0].size());
		for(int i=0;i<m.size();i++)for(int j=0;j<a.m[0].size();j++)for(int k=0;k<m[0].size();k++)(res[i][j]+=m[i][k]*a[k][j])%=mod;
		return res;
	}
	matrix operator*=(matrix&a){return *this=*this*a;}
};
void pow(matrix&res,matrix a,int n){
	while(n){
		if(n&1)res*=a;
		a*=a;
		n>>=1;
	}
}
int pow(int a,int n){
	int res=1;
	while(n){
		if(n&1)res=res*a%mod;
		a=a*a%mod;
		n>>=1;
	}
	return res;
}
void solve(){
	int n,c;
	cin>>n>>c;
	vector<int>v(n);
	cin>>v;
	matrix m1(1,n),m2(n,n);
	for(int i=0;i<n;i++)m1[0][i]=v[i];
	for(int i=0;i<n;i++)for(int j=i;j<n;j++)m2[i][j]=v[j];
	pow(m1,m2,c-1);
	int ans=0;
	for(int i=0;i<n;i++)ans=(ans+m1[0][i])%mod;
	for(int i=0;i<n;i++)ans=(ans+mod-pow(v[i],c))%mod;
	cout<<ans;
}
}
signed main(){
	/*freopen("spice.in","r",stdin);
	freopen("spice.out","w",stdout);*/
	int t=1;
	//cin>>t;
	while(t--)AC::solve();
}