#include<bits/stdc++.h>
using namespace std;

typedef long long ll;
const ll maxn=1e6+5, inf=1e18;

ll tot,k;
ll p[maxn][26], ed[maxn], dis[5005], dep[maxn], val[maxn], dp[5005];
map<ll,ll> E;
vector<ll> vec[maxn];

void insert(string s) {
	ll pos=0;
	for(ll i=0;i<s.size();i++) {
		ll v=s[i]-'a';
		if(!p[pos][v]) p[pos][v]=++tot;
		pos=p[pos][v];
	}
	ed[pos]=1;
	return ;
}

void dfs(ll x) {
	if(ed[x]) vec[x].push_back(x);
	val[x]=inf;
	for(ll i=0;i<26;i++) {
		if(!p[x][i]) continue;
		dep[p[x][i]]=dep[x]+1;
		dfs(p[x][i]);
		for(auto p:vec[p[x][i]]) vec[x].push_back(p);
	}
	for(auto p:vec[x]) val[x]=min(val[x],(dep[p]-dep[x]+k-1)/k+dis[((dep[x]-dep[p])%k+k)%k]);
	return ;
}

void solve() {
	ll n; cin>>n>>k;
	for(ll i=0;i<=tot;i++){
		vec[i].clear();
		ed[i]=0;
		for(ll j=0;j<26;j++) p[i][j]=0;
	}
	tot=0;
	E.clear();
	for(ll i=0;i<k;i++) dis[i]=inf;
	dis[0]=0;
	for(ll i=1;i<=n;i++) {
		string s; cin>>s;
		insert(s);
		if(E.find(s.size()%k)==E.end()||E[s.size()%k]>s.size()) E[s.size()%k]=s.size();
	}
	for(auto p:E) {
		ll y=p.first, w=p.second;
		if(!y) continue;
		ll d=__gcd(k,y);
		for(ll v=0;v<d;v++) {
			ll cnt=0;
			for(ll x=(v+y)%k;cnt<2;x=(x+y)%k,cnt+=(x==v)) dis[x]=min(dis[x],dis[(x-y+k)%k]+((x-y+k)%k+w)/k+1);
		}
	}
	dfs(0);
	string t; cin>>t;
	for(ll i=0;i<=t.size();i++) dp[i]=inf;
	dp[0]=0;
	for(ll i=0;i<t.size();i++) {
		ll x=0;
		for(ll j=i+1;j<=t.size();j++) {
			if(p[x][t[j-1]-'a']) x=p[x][t[j-1]-'a'];
			else break;
			dp[j]=min(dp[j],dp[i]+val[x]+1);
		}
	}
	if(dp[t.size()]!=inf) cout<<dp[t.size()]<<'\n';
	else cout<<"-1\n";
	return ;
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0), cout.tie(0);
	ll q; cin>>q;
	while(q--) solve();
	return 0;
}