mod = 998244353
eps = 10**-9


def main():
    import sys
    input = sys.stdin.readline

    # comb init
    nmax = 10 ** 5 + 10  # change here
    fac = [0] * nmax
    finv = [0] * nmax
    inv = [0] * nmax
    fac[0] = 1
    fac[1] = 1
    finv[0] = 1
    finv[1] = 1
    inv[1] = 1
    for i in range(2, nmax):
        fac[i] = fac[i - 1] * i % mod
        inv[i] = mod - inv[mod % i] * (mod // i) % mod
        finv[i] = finv[i - 1] * inv[i] % mod

    def comb(n, r):
        if n < r:
            return 0
        else:
            return (fac[n] * ((finv[r] * finv[n - r]) % mod)) % mod

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

        S = sum(A)
        B = [0] * N
        C = []
        for i in range(N):
            B[i] = K * A[i] // S
            C.append((i, (K * A[i]) / S - B[i]))
        C.sort(key=lambda x: x[1], reverse=True)
        SB = sum(B)
        for i in range(K - SB):
            B[C[i][0]] += 1
        ans = 1
        S_inv = pow(S, mod-2, mod)
        T = K
        for i in range(N):
            ans = (ans * pow((A[i] * S_inv)%mod, B[i], mod))%mod
            ans = (ans * comb(T, B[i]))%mod
            T -= B[i]
        print(ans)


if __name__ == '__main__':
    main()