#include <bits/stdc++.h>

using namespace std;
#define int long long
const int p=998244353;
int po(int a,int b) {if(b==0) return 1; if(b==1) return a; if(b%2==0) {int u=po(a,b/2);return (u*u)%p;} else {int u=po(a,b-1);return (a*u)%p;}}
int inv(int x) {return po(x,p-2);}
const int maxn=4e5+5;
int fact[maxn];int invf[maxn];
int c1(int n,int k)
{
    if(n<k || n<0 || k<0) return 0;
    int res=fact[n];res*=invf[k];res%=p;res*=invf[n-k];res%=p;return res;
}
int32_t main()
{
    ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
    fact[0]=1;for(int i=1;i<maxn;++i) {fact[i]=(fact[i-1]*i)%p;} for(int i=0;i<maxn;++i) invf[i]=inv(fact[i]);
    int t;cin>>t;
    while(t--)
    {
        int n,m;cin>>n>>m;int a[n];for(int i=0;i<n;++i) cin>>a[i];
        map<int,int> u;for(int i=0;i<n;++i) u[a[i]]++;
        vector<pair<int,int> > v;for(auto [key,val]:u) v.push_back({key,val});
        sort(v.begin(),v.end());reverse(v.begin(),v.end());
        int l=n,r=n;
        int res=1;int tot=0;int rem=v.size();
        for(auto [ma,c]:v)
        {
            --rem;
            if(ma==r-c && 2*(r-c)+c>=n)
            {
                ++tot;
                if(l==r && rem) {res*=2;res%=p;}
                r-=c;
            }
            else if(ma==l-c && 2*(l-c)+c>=n)
            {
                ++tot;
                l-=c;
            }
            else
            {
                int h=(l+r-c);
                if(h%2==1) {res*=0;res%=p;}
                if(h!=2*ma) {res*=0;res%=p;}
                tot+=2;
                int o=l-h/2;
                res*=c1(c,o);res%=p;
                l=h/2;r=h/2;
            }
        }
        res*=c1(m,tot);res%=p;
        cout<<(res%p+p)%p<<'\n';
    }
    return 0;
}