#include <bits/stdc++.h>
using namespace std;
void _main();
int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	_main();
	return 0;
}
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using vi = std::vector<int>;
using vvi = std::vector<vi>;
using vl = std::vector<ll>;
using vii = std::vector<pair<int, int> >;
using vvl = std::vector<vl>;
using vll = std::vector<pair<ll , ll> >;
using vd = std::vector<double>;
using vvd = std::vector<vd>;
using vs = std::vector<std::string>;
using vvs = std::vector<vs>;
using vb = std::vector<bool>;
using vvb = std::vector<vb>;
using vc = std::vector<char>;
using vvc = std::vector<vc>;
using pii = std::pair<int, int>;
using pll = std::pair<ll, ll>;
using piil = std::pair<pair<int, int>, ll>;
using mii = std::map<int, int>;
using mll = std::map<ll, ll>;
using pql = std::priority_queue<ll>;
using pqi = std::priority_queue<int>;
using pqiil = std::priority_queue<pair<pair<int, int>, ll> >;
using pqii = std::priority_queue<pair<int, int> >;

#define pb push_back
#define ps push
#define eb emplace_back
#define is insert
#define er erase
#define f first
#define s second
#define lb lower_bound
#define ub upper_bound
#define sf(i) sizeof(i)
#define endl "\n"
#define sz(v) ((int)(v).size())
#define all(v) (v).begin(), (v).end()
#define rep(i, L, R) for(ll i = L;i<=R;i++)
#define pcis precision

template<typename T>
struct infinity {
	static constexpr T max=std::numeric_limits<T>::max();
	static constexpr T min=std::numeric_limits<T>::min();
	static constexpr T value=std::numeric_limits<T>::max()/2;
	static constexpr T mvalue=std::numeric_limits<T>::min()/2;
};
template<typename T>constexpr T INF=infinity<T>::value;
constexpr ll lINF=INF<ll>;
constexpr int iINF = INF<int>;
constexpr ld PI = 3.1415926535897932384626;

ull fpow(ll x, ll y, ll mod) {
	if (!y) return 1%mod;
	x %= mod;
	ll ret = 1;
	while(y > 0) {
		if(y%2 == 1) ret = (ret*x)%mod;
		x = (x*x)%mod;
		y /= 2;
	}
	return (ull)ret;
}
ll MOD = 998244353;

void _main() {
	
	ll T;
	cin >> T;
	while (T--) {
		ll N, K;
		cin >>N>>K;
		ll RES = 1;
		for (ll i = 1;i<=N;i++) {
			ll A;
			cin >> A;
			RES *= fpow(K, i*(A-1), MOD);
			RES %= MOD;
			RES *= (fpow(K, i, MOD)-1)+MOD;
			RES %= MOD;
		}
		cout <<RES << endl;
	}
	
	
	
	
	
	
	
	
}