SIZE=10**5+10; MOD=998244353 #ここを変更する

inv = [0]*SIZE  # inv[j] = j^{-1} mod MOD
fac = [0]*SIZE  # fac[j] = j! mod MOD
finv = [0]*SIZE # finv[j] = (j!)^{-1} mod MOD
fac[0] = fac[1] = 1
finv[0] = finv[1] = 1
for i in range(2,SIZE):
    fac[i] = fac[i-1]*i%MOD
finv[-1] = pow(fac[-1],MOD-2,MOD)
for i in range(SIZE-1,0,-1):
    finv[i-1] = finv[i]*i%MOD
    inv[i] = finv[i]*fac[i-1]%MOD

def choose(n,r): # nCk mod MOD の計算
    if 0 <= r <= n:
        return (fac[n]*finv[r]%MOD)*finv[n-r]%MOD
    else:
        return 0

def chofuku(box,ball): # nHk mod MOD の計算
    if box == ball == 0: return 1
    return choose(box+ball-1,ball)

def perm(n,r): # nPr mod MOD
    if 0 <= r <= n:
        return fac[n]*finv[n-r]%MOD
    else:
        return 0




from heapq import *

def solve(n,k,a):
    sa = sum(a)
    a.sort(reverse=1)
    pa = [ai/sa for ai in a]
    # 確率、回数、index
    q = [(-ai,0,i) for i,ai in enumerate(pa)]
    for _ in range(k):
        p,c,idx = heappop(q)
        p = -pa[idx]/(c+2)
        heappush(q,(p,c+1,idx))

    ans = pow(sa,MOD-1-k,MOD)*fac[k]%MOD
    for _,c,i in q:
        ans *= pow(a[i],c,MOD)
        ans %= MOD
        ans *= finv[c]
        ans %= MOD
    return ans

import sys
readline = sys.stdin.readline

T = int(input())
for _ in range(T):
    n,k = map(int,readline().split())
    *a, = map(int,readline().split())
    ans = solve(n,k,a)
    print(ans)