#include<iostream>
#include<cassert>
#include<atcoder/modint>
using namespace std;
#include<vector>
template<typename T>
struct combination{
	vector<T>fac,ifac;
	combination(size_t N=0):fac(1,1),ifac(1,1)
	{
		make_table(N);
	}
	void make_table(size_t N)
	{
		if(fac.size()>N)return;
		size_t now=fac.size();
		N=max(N,now*2);
		fac.resize(N+1);
		ifac.resize(N+1);
		for(size_t i=now;i<=N;i++)fac[i]=fac[i-1]*i;
		ifac[N]=1/fac[N];
		for(size_t i=N;i-->now;)ifac[i]=ifac[i+1]*(i+1);
	}
	T factorial(size_t n)
	{
		make_table(n);
		return fac[n];
	}
	T invfac(size_t n)
	{
		make_table(n);
		return ifac[n];
	}
	T P(size_t n,size_t k)
	{
		if(n<k)return 0;
		make_table(n);
		return fac[n]*ifac[n-k];
	}
	T C(size_t n,size_t k)
	{
		if(n<k)return 0;
		make_table(n);
		return fac[n]*ifac[n-k]*ifac[k];
	}
	T H(size_t n,size_t k)
	{
		if(n==0)return k==0?1:0;
		return C(n-1+k,k);
	}
};
using mint=atcoder::modint998244353;
combination<mint>C;
int N,KK;
long A[2<<17];
mint naive(int id,int jd,mint cur)
{
	assert(jd<=id);
	if(id==0)return cur;
	if(id==jd)
	{
		if(A[id]!=0)return 0;
		return naive(id-1,0,cur);
	}
	mint ret=0;
	for(int t=0;t<=A[id];t++)
	{
		A[id]-=t;
		A[jd]+=t;
		ret+=naive(id,jd+1,t==0?cur:cur*(mint(KK).pow(t)-mint(KK).pow(t-1)));
		A[id]+=t;
		A[jd]-=t;
	}
	return ret;
}
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int T;cin>>T;
	for(;T--;)
	{
		cin>>N>>KK;
		long sum=0;
		for(int i=1;i<=N;i++)
		{
			cin>>A[i];
			sum+=(long)i*A[i];
		}
		mint K=KK;
		mint rp=(K-1)/K,rn=(K+1)/K;
		/*
		mint ans=0;
		ans+=K.pow(A[2])*rn*K.pow(A[0]+2*A[1])*rn*rn*rp;//a=0, b=0
		ans+=K.pow(A[2])*rn*K.pow(A[0]+2*A[1]+A[2])*rn*rn*rp;//b=0, c=0
		ans+=K.pow(A[2])*rn*K.pow(A[0]+2*A[1]+2*A[2])*rn*rn*rp;//a=0, c=0
		ans+=K.pow(A[2])*rn*rn*K.pow(A[0]+2*A[1])*(K.pow(2*A[2]-2)-1)*rn;

		ans+=K.pow(A[2])*rn*K.pow(A[0]+2*A[1])*rn*rp;
		*/
		//cout<<"naive = "<<naive(N,0,1).val()<<" ";
		mint t=1,p=1;
		long long c=0,nowc=0;
		for(int i=1;i<=N;i++)
		{
			t*=p;
			c+=nowc++;
			p+=K.pow(i);
		}
		cout<<(mint(K).pow(sum)*rp.pow(N)*K.inv().pow(c)*t).val()<<"\n";
	}
}