import sys
input = lambda : sys.stdin.readline().rstrip()

sys.setrecursionlimit(2*10**5+10)
write = lambda x: sys.stdout.write(x+"\n")
debug = lambda x: sys.stderr.write(x+"\n")

t = int(input())
items = []
N = 100
M = 998244353
sn = sk = 0
for _ in range(t):
    n,k = list(map(int, input().split()))
    a = list(map(int, input().split()))
    N = max(N, n+k+10)
    items.append((n,k,a))
    sn += n
    sk += k
    assert all(1<=v<=1000 for v in a)
    assert 1<=n<=10**5
    assert 1<=k<=10**5
assert 1<=t<=100
assert sn<=10**5
assert sk<=10**5

g1 = [0] * (N+1) # 元テーブル
g2 = [0] * (N+1) #逆元テーブル
inverse = [0] * (N+1) #逆元テーブル計算用テーブル
g1[0] = g1[1] = g2[0] = g2[1] = 1
inverse[0], inverse[1] = [0, 1]
for i in range( 2, N + 1 ):
    g1[i] = ( g1[i-1] * i ) % M 
    inverse[i] = ( -inverse[M % i] * (M//i) ) % M # ai+b==0 mod M <=> i==-b*a^(-1) <=> i^(-1)==-b^(-1)*aより
    g2[i] = (g2[i-1] * inverse[i]) % M 
    
ans = []
for n,k,a in items:
    from heapq import heappop as hpp, heappush as hp, heapify
    h = [(-v,i) for i,v in enumerate(a)]
    heapify(h)
    x = [0]*n
    for _ in range(k):
        v,i = hpp(h)
        v *= -1
        x[i] += 1
        hp(h, (-a[i]/(x[i]+1), i))
    val = g1[k]
    for i in range(n):
        val *= (pow(a[i], x[i], M) * g2[x[i]] % M)
        val %= M
    val *= pow(pow(sum(a), k, M), M-2, M)
    ans.append(val%M)
write("\n".join(map(str, ans)))