(defpackage :codeforces
  (:use :cl :sb-int))
(in-package :codeforces)

(declaim (optimize (speed 3) (safety 0)))

(defun modint998 (x)
  (mod x 998244353))

(defun mint-pow (x n)
  (let ((result 1)
        (base (modint998 x)))
    (loop while (> n 0) do
          (when (oddp n)
            (setf result (modint998 (* result base))))
          (setf base (modint998 (* base base)))
          (setf n (floor n 2)))
    result))

(defun solve (n k a)
  (let ((ans 1))
    (loop for i from 1 to n do
          (setf ans (modint998 (* ans (- (mint-pow k i) 1)))))
    (loop for i from 0 below n do
          (setf ans (modint998 (* ans (mint-pow k (* (+ i 1) (1- (aref a i))))))))
    (princ ans) (terpri)))

(defun main ()
  (let ((num-cases (read)))
    (loop for _ from 1 to num-cases do
          (let* ((n (read))
                 (k (read))
                 (a (make-array n :initial-contents (loop for _ from 1 to n collect (read)))))
            (solve n k a)))))

(main)