#include <bits/stdc++.h>
#define x first
#define y second
using namespace std;
using pii=pair<int,int>;
using ll=long long;
using vi=vector<int>;
using vl=vector<ll>;
#define pb push_back
#define all(a) begin(a),end(a)

const int N=5010,MOD=1e9+7,B1=32984723,B2=345932;
const char en='\n';
const ll LLINF=1ll<<60;

void ad(int&a,int b)
{
	a+=b;
	if (a>=MOD) a-=MOD;
}

int add(int a,int b)
{
	if (a+b>=MOD) return a+b-MOD;
	return a+b;
}

void su(int&a,int b)
{
	a-=b;
	if (a<0) a+=MOD;
}

int sub(int a,int b)
{
	if (a<b) return a-b+MOD;
	return a-b;
}

int mul(int a,int b)
{
	return (a*1ll*b)%MOD;
}

int pot(int n,int k)
{
	if (k==0) return 1;
	int r=pot(n,k/2);
	r=mul(r,r);
	if (k%2) r=mul(r,n);
	return r;
}

using hashtype=pii;

void dod(hashtype&a,char c)
{
	a={add(mul(a.x,B1),c),add(mul(a.y,B2),c)};
	//a=add(mul(a,B1),c);
}

const bool DEB=0;
string re;
ll t,di[N],rr[N],n,k,dp[N],di2[N][N];
hashtype hashdef;
bool bio[N];

int main()
{
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	if (DEB) t=1;
	else cin>>t;
	while (t--)
	{
		if (DEB) n=5e4,k=5000;
		else cin>>n>>k;
		vector<string> v(n);
		for (auto&x: v)
		{
			if (DEB)
			{
				x="";
				for (int z=0;z<19;++z) x.pb(rand()%26+'a');
			}
			else cin>>x;
		}
		if (DEB)
		{
			re="";
			for (int i=0;i<5000;++i) re.pb(rand()%26+'a');
		}
		else cin>>re;
		for (int i=0;i<k;++i) di[i]=LLINF,rr[i]=LLINF,bio[i]=0;
		for (auto x: v) di[x.size()%k]=min(di[x.size()%k],(int)x.size()+k);
		rr[0]=0;
		for (int z=0;;++z)
		{
			ll nm=LLINF;
			int kak=-1;
			for (int i=0;i<k;++i) if (!bio[i] && rr[i]<nm)
			{
				nm=rr[i];
				kak=i;
			}
			if (kak==-1) break;
			bio[kak]=1;
			for (int i=kak;i<k;++i) rr[i]=min(rr[i],rr[kak]+di[i-kak]);
			for (int i=0;i<kak;++i) rr[i]=min(rr[i],rr[kak]+di[i+k-kak]);
		}
		vector<pair<hashtype,ll>> mo;
		for (auto x: v)
		{
			hashtype ha=hashdef;
			int xs=x.size();
			for (int i=0;i<xs;++i)
			{
				dod(ha,x[i]);
				int moo=((i+1-xs)%k+k)%k;
				if (rr[moo]==LLINF) continue;
				ll co=(rr[moo]+xs-(i+1))/k+1;
				//cout<<x<<' '<<i+1<<' '<<co<<' '<<moo<<' '<<rr[moo]<<en;
				mo.pb({ha,co});
			}
		}
		sort(all(mo));
		int rs=re.size();
		for (int i=0;i<=rs;++i) dp[i]=LLINF;
		vector<pair<hashtype,int>> sv;
		sv.reserve(rs*(rs+1)/2);
		for (int i=0;i<rs;++i)
		{
			hashtype ha=hashdef;
			for (int j=i;j<rs;++j)
			{
				dod(ha,re[j]);
				sv.pb({ha,i*rs+j});
				di2[i][j]=LLINF;
			}
		}
		sort(all(sv));
		int p1=0;
		for (auto x: sv)
		{
			while (p1<(int)mo.size() && mo[p1].x<x.x) ++p1;
			if (p1<(int)mo.size() && mo[p1].x==x.x) di2[x.y/rs][x.y%rs]=mo[p1].y;
		}
		dp[0]=0;
		for (int i=0;i<rs;++i)
		{
			for (int j=i;j<rs;++j)
			{
				dp[j+1]=min(dp[j+1],dp[i]+di2[i][j]);
			}
		}
		if (dp[rs]==LLINF) cout<<-1<<en;
		else cout<<dp[rs]<<en;
	}
}