from heapq import *
mod = 998244353
fact = [1,1]
finv = [1,1]
inv = [0,1]
 
for i in range(2,10**5+5):
    fact.append((fact[-1]*i)%mod)
    inv.append((inv[mod%i]*(mod-mod//i))%mod)
    finv.append((finv[-1]*inv[-1])%mod)
def solve():
    n,k = map(int,input().split())
    A = list(map(int,input().split()))
    X = [0]*n
    h = [[-a,i] for i,a in enumerate(A)]
    heapify(h)
    for _ in range(k):
        v,i = heappop(h)
        X[i] += 1
        heappush(h,[-A[i]/(X[i]+1),i])
    
    ans = fact[k]
    for i,(x,a) in enumerate(zip(X,A)):
        ans *= pow(a,x,mod)*finv[x]%mod
        ans %= mod
    base = pow(sum(A),k,mod)
    ans *= pow(base,mod-2,mod)
    ans %= mod
    print(ans)

t = int(input())
for _ in range(t):
    solve()