import java.io.IOException;
import java.io.InputStream;
import java.util.Arrays;
import java.util.NoSuchElementException;
import java.util.PriorityQueue;

public class Main {
	public static void main(String[] args) {
		new Main().run();
	}
	
	long gcd(long a, long b) {
		return b==0?a:gcd(b,a%b);
	}
	
	class Q implements Comparable<Q>{
		long n;
		long d;
		public Q(long n, long d) {
			this.n=n;
			this.d=d;
		}
		@Override
		public int compareTo(Main.Q o) {
			return Long.compare(-(n*o.d-o.n*d), 0);
		}
	}
	
	final long p=998244353;
	
	long[] inv=new long[1000000];
	{
		inv[0]=inv[1]=1;
		for (int i=2;i<inv.length;++i) inv[i]=p-(p/i)*inv[(int)(p%i)]%p;
	}
	
	long pow(long a, long n) {
		return n==0?1:pow(a*a%p,n/2)*(n%2==1?a:1)%p;
	}
	
	long inv(long a) {
		return pow(a, p-2);
	}
	
	void run() {
		Scanner sc = new Scanner();
		int T=sc.nextInt();
		while (T-->0) {
			int N=sc.nextInt();
			int K=sc.nextInt();
			long[] A=new long[N];
			for (int i=0;i<N;++i) {
				A[i]=sc.nextLong();
			}
			long sumA=0;
			for (long a:A) sumA=(sumA+a)%p;
			PriorityQueue<Q> pq=new PriorityQueue<>();
			for (long a:A) {
				pq.add(new Q(a,1));
			}
			long ans=1;
			for (int i=0;i<K;++i) {
				Q q=pq.poll();
				ans=ans*q.n%p*inv(q.d)%p*inv(sumA)%p;
				pq.add(new Q(q.n,q.d+1));
			}
			for (long i=1;i<=K;++i) ans=ans*i%p;
			System.out.println(ans);
		}
	}

	class Scanner {
		private final InputStream in = System.in;
		private final byte[] buffer = new byte[1024];
		private int ptr = 0;
		private int buflen = 0;

		private boolean hasNextByte() {
			if (ptr < buflen) {
				return true;
			} else {
				ptr = 0;
				try {
					buflen = in.read(buffer);
				} catch (IOException e) {
					e.printStackTrace();
				}
				if (buflen <= 0) {
					return false;
				}
			}
			return true;
		}

		private int readByte() {
			if (hasNextByte())
				return buffer[ptr++];
			else
				return -1;
		}

		private boolean isPrintableChar(int c) {
			return 33 <= c && c <= 126;
		}

		public boolean hasNext() {
			while (hasNextByte() && !isPrintableChar(buffer[ptr]))
				ptr++;
			return hasNextByte();
		}

		public String next() {
			if (!hasNext())
				throw new NoSuchElementException();
			StringBuilder sb = new StringBuilder();
			int b = readByte();
			while (isPrintableChar(b)) {
				sb.appendCodePoint(b);
				b = readByte();
			}
			return sb.toString();
		}

		public long nextLong() {
			if (!hasNext())
				throw new NoSuchElementException();
			long n = 0;
			boolean minus = false;
			int b = readByte();
			if (b == '-') {
				minus = true;
				b = readByte();
			}
			if (b < '0' || '9' < b) {
				throw new NumberFormatException();
			}
			while (true) {
				if ('0' <= b && b <= '9') {
					n *= 10;
					n += b - '0';
				} else if (b == -1 || !isPrintableChar(b)) {
					return minus ? -n : n;
				} else {
					throw new NumberFormatException();
				}
				b = readByte();
			}
		}

		public int nextInt() {
			long nl = nextLong();
			if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE)
				throw new NumberFormatException();
			return (int) nl;
		}

		public double nextDouble() {
			return Double.parseDouble(next());
		}

	}

	static void tr(Object... objects) {
		System.out.println(Arrays.deepToString(objects));
	}
}