package yukicoder;

import java.util.*;

public class Q444 {
	static final long MODULO = 1_000_000_000 + 7;

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		long c = sc.nextLong();
		long[] a = new long[n];
		for (int i = 0; i < n; ++i) {
			a[i] = sc.nextLong() % MODULO;
		}
		long[][] vec = new long[n][1];
		for (int i = 0; i < n; ++i) {
			vec[i][0] = 1;
		}
		long[][] mx = new long[n][n];
		for (int i = 0; i < n; ++i) {
			for (int j = 0; j <= i; ++j) {
				mx[i][j] = a[j];
			}
		}
		vec = pow(mx, vec, c);
		long ans = vec[n - 1][0];
		for (int i = 0; i < n; ++i) {
			ans = (ans - pow(a[i], c) + MODULO) % MODULO;
		}
		System.out.println(ans);
	}

	static long[][] pow(long[][] mx, long[][] vec, long n) {
		for (; n > 0; n >>= 1, mx = mul(mx, mx)) {
			if (n % 2 == 1) {
				vec = mul(mx, vec);
			}
		}
		return vec;
	}

	static long pow(long a, long n) {
		long ret = 1;
		for (; n > 0; n >>= 1, a = (a * a) % MODULO) {
			if (n % 2 == 1) {
				ret = (ret * a) % MODULO;
			}
		}
		return ret;
	}

	static long[][] mul(long[][] A, long[][] B) {
		if (A[0].length != B.length)
			throw new AssertionError();
		int mid = A[0].length;
		long[][] ret = new long[A.length][B[0].length];
		for (int i = 0; i < A.length; ++i) {
			for (int j = 0; j < B[0].length; ++j) {
				for (int k = 0; k < mid; ++k) {
					ret[i][j] += A[i][k] * B[k][j] % MODULO;
					ret[i][j] %= MODULO;
				}
			}
		}
		return ret;
	}

	static void tr(Object... objects) {
		System.out.println(Arrays.deepToString(objects));
	}
}