use std::cmp::Ordering;
use std::cmp;
use std::cmp::min;
use std::collections::BTreeMap;
use std::process;
use std::cmp::Ord;
use std::collections::HashMap;
use std::collections::HashSet;
use std::collections::VecDeque;
use std::collections::BTreeSet;
use std::mem;
use std::collections::BinaryHeap;
use std::hash::{Hash, Hasher};

pub struct Scanner<R> {
    stdin: R,
}
 
impl<R: std::io::Read> Scanner<R> {
    pub fn read<T: std::str::FromStr>(&mut self) -> T {
        use std::io::Read;
        let buf = self
            .stdin
            .by_ref()
            .bytes()
            .map(|b| b.unwrap())
            .skip_while(|&b| b == b' ' || b == b'\n' || b == b'\r')
            .take_while(|&b| b != b' ' && b != b'\n' && b != b'\r')
            .collect::<Vec<_>>();
        std::str::from_utf8(&buf).unwrap()
            .parse()
            .ok()
            .expect("Parse error.")
    }
    pub fn vec<T: std::str::FromStr>(&mut self, n: usize) -> Vec<T> {
        (0..n).map(|_| self.read()).collect()
    }
    pub fn chars(&mut self) -> Vec<char> {
        self.read::<String>().chars().collect()
    }
}


pub trait BinarySearch<T> {
    fn lower_bound(&self, x:&T) -> usize;
    fn upper_bound(&self, x:&T) -> usize;
}

impl<T: Ord> BinarySearch<T> for VecDeque<T>{
    fn lower_bound(&self, x: &T) -> usize {
        let mut low = 0;
        let mut high = self.len();

        while low != high {
            let mid = (low + high) / 2;
            match self[mid].cmp(x) {
                Ordering::Less => {
                    low = mid + 1;
                }
                Ordering::Equal | Ordering::Greater => {
                    high = mid;
                }
            }
        }
        low
    }

    fn upper_bound(&self, x: &T) -> usize {
        let mut low = 0;
        let mut high = self.len();

        while low != high {
            let mid = (low + high) / 2;
            match self[mid].cmp(x) {
                Ordering::Less | Ordering::Equal => {
                    low = mid + 1;
                }
                Ordering::Greater => {
                    high = mid;
                }
            }
        }
        low
    }
}
impl<T: Ord> BinarySearch<T> for [T]{
    fn lower_bound(&self, x: &T) -> usize {
        let mut low = 0;
        let mut high = self.len();

        while low != high {
            let mid = (low + high) / 2;
            match self[mid].cmp(x) {
                Ordering::Less => {
                    low = mid + 1;
                }
                Ordering::Equal | Ordering::Greater => {
                    high = mid;
                }
            }
        }
        low
    }

    fn upper_bound(&self, x: &T) -> usize {
        let mut low = 0;
        let mut high = self.len();

        while low != high {
            let mid = (low + high) / 2;
            match self[mid].cmp(x) {
                Ordering::Less | Ordering::Equal => {
                    low = mid + 1;
                }
                Ordering::Greater => {
                    high = mid;
                }
            }
        }
        low
    }
}
fn comb(a:usize, b:usize,  fac:&Vec<usize>, ifac:&Vec<usize>)->usize{
        let mut a = a;
        let mut b = b;
        if a == 0 && b == 0{return 1;}
        if a<b || a<0{return 0;}
        let mut tmp = ifac[a-b]*ifac[b]%MODu;
        return tmp * fac[a]%MODu;
}
fn nHr(n:usize, r:usize, fac:&Vec<usize>, ifac:&Vec<usize>)->usize{
    return comb(n+r-1, r, fac, ifac);
}
fn modinv(a:usize, M:usize)->usize{
    let mut b = M as i64;
    let mut u = 1 as i64;
    let mut v = 0 as i64;
    let mut a = a as i64;
    let mut m = M as i64;
    while(b>0){
        let mut t = a/b;
        a -= t*b;
        mem::swap(&mut a, &mut b);
        u-=t*v;
        mem::swap(&mut u, &mut v);
    }
    u%=m;
    if u<0{u+=m;}
    return u as usize;

}
fn modpow(x:usize, n:usize) -> usize{
        let mut ans = 1;
        let mut n = n as usize;
        let mut x = x;
        while(n != 0){
            if (n&1 == 1){ans = ans*x%MODu;}
            x = x*x%MODu;
            n = n>>1;
        }
        ans
}
fn invs(max:usize)->(Vec<usize>, Vec<usize>){
    let mut fac = vec![0;max+1];
    let mut ifac = vec![0;max+1];
    fac[0] = 1;
    ifac[0] = 1;
    for i in 0..max{

        fac[i+1] = fac[i] * (i+1)%MODu;
        ifac[i+1] = ifac[i] * modpow(i+1, MODu - 2)%MODu;
    }
    (fac, ifac)
}
fn solve(){
    let sssss = std::io::stdin();
    let mut sc = Scanner { stdin: sssss.lock() };
    let mut test:usize = sc.read();
    for _ in 0..test{
        let mut N:usize = sc.read();
        let mut K:usize = sc.read();
        let mut A = vec![0i64;N];
        let mut s = 0;
        for i in 0..N{
            A[i] = sc.read();
            s+=A[i];
        }
        let mut bh = BinaryHeap::new();
        for i in 0..N{
            bh.push((A[i], 0, 1, A[i]));
        }
        let mut res = 1;
        for i in 0..K{
            let mut t = bh.pop().unwrap();
            let mut a = t.0;
            let mut b = t.1;
            let mut c = t.2;
            let mut d = t.3;
            let mut tmp = (d*modinv(c as usize, MOD as usize) as i64)%MOD;
            res *= tmp;
            res%=MOD;
            c+=1;
            bh.push(((d/c), (d%c), c, d));
        }
        for i in 1..K as i64 + 1{
            res*=i;
            res%=MOD;
            res*=modinv(s as usize, MOD as usize) as i64;
            res%=MOD;
        }
        println!("{}", res);
    }













    














} 





    
fn main(){
    solve();
}


const PI:f64 = std::f64::consts::PI;
pub static MOD:i64    = 998244353;
pub static MODu:usize = 998244353;
pub static MODi32:i32 = 1000000007;
pub static eps:f64 = 1e-6;
const INF: i64 = 1 << 60;
const INFu:usize = 1<<56;
const INFu128:u128 = 1<<126;