#include <bits/stdc++.h>

#define _overload(_1,_2,_3,name,...) name
#define _rep(i,n) _range(i,0,n)
#define _range(i,a,b) for(int i=int(a);i<int(b);++i)
#define rep(...) _overload(__VA_ARGS__,_range,_rep,)(__VA_ARGS__)

#define _rrep(i,n) _rrange(i,n,0)
#define _rrange(i,a,b) for(int i=int(a)-1;i>=int(b);--i)
#define rrep(...) _overload(__VA_ARGS__,_rrange,_rrep,)(__VA_ARGS__)

#define _all(arg) begin(arg),end(arg)
#define uniq(arg) sort(_all(arg)),(arg).erase(unique(_all(arg)),end(arg))
#define getidx(ary,key) lower_bound(_all(ary),key)-begin(ary)
#define clr(a,b) memset((a),(b),sizeof(a))
#define bit(n) (1LL<<(n))
#define popcount(n) (__builtin_popcountll(n))

using namespace std;

template<class T>bool chmax(T &a, const T &b) { return (a<b)?(a=b,1):0;}
template<class T>bool chmin(T &a, const T &b) { return (b<a)?(a=b,1):0;}

using ll=long long;
using R=long double;
const R EPS=1e-9; // [-1000,1000]->EPS=1e-8 [-10000,10000]->EPS=1e-7
inline int sgn(const R& r){return(r > EPS)-(r < -EPS);}
inline R sq(R x){return sqrt(max<R>(x,0.0));}

const int dx[8]={1,0,-1,0,1,-1,-1,1};
const int dy[8]={0,1,0,-1,1,1,-1,-1};

// Problem Specific Parameter:
const ll mod=1000000007LL;

using vec=valarray<ll>;
using mat=valarray<vec>;

mat mul(mat a,mat b){
	const int m=a.size();
	mat c(vec(0LL,m),m);
	rep(i,m)rep(j,m) rep(k,m) c[i][j]=(c[i][j]+1LL*a[i][k]*b[k][j])%mod;
	return c;
}

mat power(mat a,ll n){
	int m=a.size();
	mat b(vec(0LL,m),m);
	rep(i,m) b[i][i]=1LL;
	
	while(n){
		if(n&1) b=mul(b,a);
		a=mul(a,a);
		n>>=1;
	}
	return b;
}

ll power(ll a,ll n){
	ll b=1LL;
	while(n){
		if(n&1) b=b*a%mod;
		a=a*a%mod;
		n>>=1;
	}
	return b;
}

int main(void){
	ll n,c;
	cin >> n >> c;
	
	vector<ll> a(n,0LL);
	mat b(vec(0LL,n),n);

	rep(i,n){
		cin >> a[i];
		rep(j,i+1) b[i][j]=a[i];
	}

	b=power(b,c);
	
	ll ans=0LL;
	rep(i,n) ans=(ans+b[i][0])%mod;
	rep(i,n) ans=(ans+mod-power(a[i],c))%mod;
	cout << ans << endl;

	return 0;
}