#include <bits/stdc++.h>
using namespace std; typedef long long ll; typedef unsigned long long ull; typedef double db;

#define int ll

const int N = 4e5 + 10, Mod = 998244353;

mt19937 mt( (ull)( &N ) );
int Rand ( int l, int r ) { return uniform_int_distribution<int>(l,r)(mt); }

int Pow ( int x, int y )
{   int res = 1; for( ; y; y >>= 1, x = x * x % Mod ) if( y&1 ) res = res * x % Mod; return res; }

int Inv ( int x ) { return Pow( x, Mod - 2 ); }

int deg, k, rad[N], W[2][N];

void Init ( int n )
{
    deg = 1, k = 0; 
    while( deg <  n ) deg <<= 1, ++k;
    for( int i = 0; i < deg; ++i ) rad[i] = ( rad[i>>1] >> 1 ) | ( i & 1 ) << ( k - 1 );
    W[0][0] = W[1][0] = 1;
    W[0][1] = Pow( 3, ( Mod - 1 ) / deg ), W[1][1] = Inv( W[0][1] );
    for( int i = 2; i <  deg; ++i ) W[0][i] = W[0][i-1] * W[0][1] % Mod, W[1][i] = W[1][i-1] * W[1][1] % Mod;
}

struct Poly : vector <int> 
{
    using vector :: vector;
    Poly cut ( int x ) const { return Poly{ begin(), begin() + min( x, (int)size() ) }; }

    friend void NTT ( Poly & F, int opt )
    {
        F.resize( deg );
        for( int i = 0; i < deg; ++i ) if( i < rad[i] ) ::swap( F[i], F[ rad[i] ] );
        for( int w = deg >> 1, m = 1; m < deg; m <<= 1, w >>= 1 )
            for( int i = 0; i < deg; i += (m << 1) ) for( int j = 0; j < m; ++j )
            {
                int x = F[i+j];
                int y = W[opt][w*j] * F[i+j+m] % Mod;
                F[i + j] = ( x + y ) % Mod; F[i + j + m] = ( x - y + Mod ) % Mod;
            }
        if( opt == 1 ) for( int inv = ::Inv(deg), i = 0; i <  deg; ++i ) F[i] = F[i] * inv % Mod;
    }

    friend Poly operator * ( const Poly& F, const Poly& G )
    {
        Init( F.size() + G.size() );
        Poly res, A = F, B = G;
        res.resize( deg );
        NTT( A, 0 );
        NTT( B, 0 );
        for( int i = 0; i < deg; ++i ) res[i] = A[i] * B[i] % Mod;
        NTT( res, 1 );
        return res;
    }
};

int n, m, w, A[N];

int fac[N], ifac[N];

int C ( int n, int m ) { return fac[n] * ifac[m] % Mod * ifac[n-m] % Mod; }

void Solve ()
{
    cin >> n >> m;

    w = n * m;
    for( int i = 1; i <= w; ++i ) cin >> A[i]; sort( A + 1, A + w + 1 );
    
    fac[0] = 1;
    for( int i = 1; i <= w; ++i ) fac[i] = fac[i-1] * i % Mod;
    ifac[0] = 1;
    for( int i = 1; i <= w; ++i ) ifac[i] = Inv( fac[i] );

    Poly F;
    F.resize( w + 5 );
    for( int i = 0; i <= n; ++i ) for( int j = 0; j <= m; ++j )
    {
        int val = ( C( n, i ) * C( m, j ) % Mod * ( ( i + j ) & 1 ? -1 : 1 ) + Mod ) % Mod;
        F[ ( n - i ) * ( m - j ) ] = ( F[ ( n - i ) * ( m - j ) ] + val ) % Mod;
    }
    for( int i = 0; i <= w; ++i ) F[i] = F[i] * fac[i] % Mod;

    Poly G;
    G.resize( w + 5 );
    for( int i = 0; i <= w; ++i ) G[i] = ( A[i] - A[i+1] + Mod ) % Mod * fac[i] % Mod;

    F = F * G;
    
    int res = 0;
    for( int i = w; i <= w * 2; ++i ) res = ( res + F[i] * ifac[i-w] % Mod ) % Mod;

    cout << ( Mod - res ) % Mod << "\n";
}

signed main()
{
    ios::sync_with_stdio( false ), cin.tie(0), cout.tie(0); int t; cin >> t; while( t-- ) Solve();
    return 0;
}