P = 998244353
nn = 202020

fa = [1] * (nn+1)
fainv = [1] * (nn+1)
for i in range(nn):
    fa[i+1] = fa[i] * (i+1) % P
fainv[-1] = pow(fa[-1], P-2, P)
for i in range(nn)[::-1]:
    fainv[i] = fainv[i+1] * (i+1) % P

C = lambda a, b: fa[a] * fainv[b] % P * fainv[a-b] % P if 0 <= b <= a else 0

T = int(input())
for _ in range(T):
    N, K = map(int, input().split())
    A = [int(a) for a in input().split()]
    su = sum(A)
    B = [K * a // su for a in A]
    su2 = sum(B)
    L = [(A[i] / (B[i] + 1), i) for i in range(N)]
    L.sort(key = lambda x: -x[0])
    for k in range(K - su2):
        i = L[k][1]
        B[i] += 1
    ans = fa[K]
    for i, b in enumerate(B):
        ans = ans * fainv[b] % P * pow(A[i], b, P) % P
    ans = ans * pow(su, (P - 2) * K, P) % P
    print(ans)