import sys # sys.setrecursionlimit(1000005) # sys.set_int_max_str_digits(200005) int1 = lambda x: int(x)-1 pDB = lambda *x: print(*x, end="\n", file=sys.stderr) p2D = lambda x: print(*x, sep="\n", end="\n\n", file=sys.stderr) def II(): return int(sys.stdin.readline()) def LI(): return list(map(int, sys.stdin.readline().split())) def LLI(rows_number): return [LI() for _ in range(rows_number)] def LI1(): return list(map(int1, sys.stdin.readline().split())) def LLI1(rows_number): return [LI1() for _ in range(rows_number)] def SI(): return sys.stdin.readline().rstrip() # dij = [(0, 1), (-1, 0), (0, -1), (1, 0)] dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)] # inf = -1-(-1 << 31) inf = -1-(-1 << 63) # md = 10**9+7 md = 998244353 from heapq import * from fractions import Fraction def inv_arr(n): if n < 1: return [] res = [-1, 1] for i in range(2, n+1): res.append(res[md%i]*(md-md//i)%md) return res inv=inv_arr(100005) n_max = 100005 fac = [1] for i in range(1, n_max+1): fac.append(fac[-1]*i%md) ifac = [1]*(n_max+1) ifac[n_max] = pow(fac[n_max], md-2, md) for i in range(n_max-1, 1, -1): ifac[i] = ifac[i+1]*(i+1)%md def solve(): n,k=LI() aa=LI() ans=fac[k]*pow(sum(aa),(md-2)*k,md)%md hp=[Fraction(1,a) for a in aa] heapify(hp) for _ in range(k): f=heappop(hp) x,a=f.numerator,f.denominator ans*=a*inv[x]%md ans%=md heappush(hp,Fraction(x+1,a)) print(ans) for _ in range(II()):solve()