import sys

# sys.setrecursionlimit(1000005)
# sys.set_int_max_str_digits(200005)
int1 = lambda x: int(x)-1
pDB = lambda *x: print(*x, end="\n", file=sys.stderr)
p2D = lambda x: print(*x, sep="\n", end="\n\n", file=sys.stderr)
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def SI(): return sys.stdin.readline().rstrip()

# dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
# inf = -1-(-1 << 31)
inf = -1-(-1 << 63)
# md = 10**9+7
md = 998244353

from heapq import *
from fractions import Fraction

def inv_arr(n):
    if n < 1: return []
    res = [-1, 1]
    for i in range(2, n+1):
        res.append(res[md%i]*(md-md//i)%md)
    return res

inv=inv_arr(100005)

n_max = 100005
fac = [1]
for i in range(1, n_max+1): fac.append(fac[-1]*i%md)
ifac = [1]*(n_max+1)
ifac[n_max] = pow(fac[n_max], md-2, md)
for i in range(n_max-1, 1, -1): ifac[i] = ifac[i+1]*(i+1)%md

def solve():
    n,k=LI()
    aa=LI()
    xx=[1]*n
    ans=fac[k]*pow(sum(aa),(md-2)*k,md)%md
    hp=[(Fraction(1,a),i) for i,a in enumerate(aa)]
    heapify(hp)
    for _ in range(k):
        f,i=heappop(hp)
        x,a=xx[i],aa[i]
        ans*=a*inv[x]%md
        ans%=md
        heappush(hp,(Fraction(x+1,a),i))
        xx[i] += 1
    print(ans)

for _ in range(II()):solve()