import sys
input = sys.stdin.readline

from heapq import heappop,heappush

mod=998244353

F=[1]
for i in range(1,200020):
    F.append(F[-1]*i%mod)

T=int(input())

for tests in range(T):
    N,K=map(int,input().split())
    A=list(map(int,input().split()))

    SUM=sum(A)
    INV=pow(SUM,mod-2,mod)

    H=[]

    for a in A:
        H.append((-a,-a*INV%mod,1))
    H.sort()

    ANS=1
    for i in range(K):
        #print(H)
        now,x,ko=heappop(H)
        ANS=ANS*(-x)%mod

        y=x*ko*pow(ko+1,mod-2,mod)%mod

        heappush(H,(now*ko/(ko+1),y,ko+1))

    #print(ANS)

    for i in range(1,K+1):
        ANS=ANS*i%mod

    print(ANS)