#pragma GCC optimize ("O3")
#pragma GCC target ("avx")
#include <bits/stdc++.h>
using namespace std;

const int mod = 1e9 + 7;

uint32_t inv;
int r2;

int reduce(uint64_t x) {
	uint64_t y = uint64_t(uint32_t(x) * inv) * mod;
	int res = int(x >> 32) - int(y >> 32);
	return res < 0 ? res + mod : res;
}

int transform(int n) {
	return reduce(1ULL * n * r2);
}

void initMontgomeryReduction() {
	inv = 1;
	for (int i = 0; i < 5; i++) {
		inv *= 2 - inv * uint32_t(mod);
	}
	r2 = -uint64_t(mod) % mod;
}

int add(int a, int b) {
	return (a += b) >= mod ? a - mod : a;
}

int mul(int a, int b) {
	return reduce(1ULL * a * b);
}

int modpow(int a, long long b) {
	int ret = 1;
	while (b > 0) {
		if (b & 1) {
			ret = 1LL * ret * a % mod;
		}
		a = 1LL * a * a % mod;
		b >>= 1;
	}
	return ret;
}

int main() {
	initMontgomeryReduction();
	int n;
	long long c;
	cin >> n >> c;
	
	long long foo = 0;
	vector<int> a(n);
	for (int i = 0; i < n; i++) {
		scanf("%d", &a[i]);
		foo += mod - modpow(a[i], c);
		a[i] = transform(a[i]);
	}

	// doubling
	// ref: https://yukicoder.me/problems/no/137

	vector<int> dp(n * 2);
	dp[0] = transform(1);
	while (c > 0) {
		for (int i = 0; i < n; i++) {
			for (int j = n * 2 - 2; j >= 0; j--) {
				dp[j + 1] = add(dp[j + 1], mul(dp[j], a[i]));
			}
		}
		int cc = c & 1;
		for (int j = 0; j < n; j++) {
			dp[j] = dp[j * 2 + cc];
		}
		for (int j = n; j < n * 2; j++) {
			dp[j] = 0;
		}
		for (int i = 0; i < n; i++) {
			a[i] = mul(a[i], a[i]);
		}
		c >>= 1;
	}

	printf("%d\n", add(reduce(dp[0]), foo % mod));
}