#include<bits/stdc++.h>

using namespace std;

#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define pf push_front
#define LC k<<1
#define RC k<<1|1
#define IO cin.sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define all(x) (x).begin(), (x).end()
#define SZ(x) ((int)(x).size())
#define rep(i,a,n) for (int i = a; i < n; i++)
#define repn(i,a,n) for (int i = a; i <= n; i++)
#define per(i,a,n) for (int i = (n) - 1; i >= a; i--)
#define pern(i,a,n) for (int i = n; i >= a; i--)

typedef long long LL;
typedef long double LD;
typedef unsigned long long ull;
typedef pair<int, int> PII;
typedef pair<int, LL> PIL;
typedef pair<LL, int> PLI;
typedef pair<double, double> PDD;
typedef pair<ull, ull> PUU;
typedef pair<LL, LL> PLL;

const int N = 1100000;
const int M = 1100000;
const int mod = 1e9+7;
const int inf = (int)1e9;
const LL INF = 1e18;
const double eps = 1e-9;

mt19937_64 Rand((unsigned long long)new char);
#define rand Rand

int T, n, m, k, pp[N], len[N], cp[N];
string s[N], t;
LL f[N], dis[N];
vector<PIL> g[N];
vector<int> tmp;
int ch[M][26], pos, rt;
LL val[M];
int newnode() {
	pos++;
	memset(ch[pos], 0, sizeof(ch[pos]));
	val[pos] = INF;
	return pos;
}
LL dp[N];
priority_queue<pair<LL, int>, vector<pair<LL, int>>, greater<pair<LL,int>>> q;
void dijkstra(int st) {
	rep(i, 0, k) dis[i] = INF, pp[i] = 0;
	dis[st] = 0;
	q.push(mp(0, st));
	while (!q.empty()) {
		int now = q.top().se; q.pop();
		if (pp[now]) continue;
		pp[now] = 1;
		for (auto p: g[now]) {
			int y = p.fi;
			LL w = p.se;
			if (dis[now] + w < dis[y]) dis[y] = dis[now] + w, q.push(mp(dis[y], y));
		}
	}
}
int main() {
	IO;
	cin >> T;
	while (T--) {
		cin >> n >> k;
		rep(i, 0, k) f[i] = INF, pp[i] = cp[i] = 0, g[i].clear();
		tmp.clear();
		repn(i, 1, n) {
			cin >> s[i];
			len[i] = s[i].size();
			f[len[i] % k] = min(f[len[i] % k], (LL)len[i]);
			if (!cp[len[i] % k]) cp[len[i] % k] = 1, tmp.pb(len[i] % k);
		}
		cin >> t;
		m = t.size();
		rep(i, 0, k) {
			for (auto j: tmp) {
				int w = f[j] / k + 1, tgt = (i + j) % k;
				if (i > tgt) w++;
				g[tgt].pb(mp(i, w));
			}
		}
		dijkstra(0);
		/*
		rep(i, 0, k) dis[i] = INF, pp[i] = 0;
		dis[0] = 0;
		while (1) {
			LL mn = INF;
			int pos = -1;
			rep(i, 0, k) if (!pp[i] && dis[i] < mn) mn = dis[i], pos = i;
			if (pos == -1) break;
			pp[pos] = 1;
			for (auto p: g[pos]) {
				int y = p.fi;
				LL w = p.se;
				dis[y] = min(dis[y], dis[pos] + w);
			}
		}
		*/
		pos = 0;
		rt = newnode();
		repn(i, 1, n) {
			int cur = rt;
			rep(j, 0, len[i]) {
				int p = s[i][j] - 'a';
				if (ch[cur][p]) cur = ch[cur][p];
				else cur = ch[cur][p] = newnode();
				int left = len[i] - j - 1;
				val[cur] = min(val[cur], dis[left % k] + left / k + 1);
			}
		}
		repn(i, 1, m) dp[i] = INF;
		dp[0] = 0;
		rep(i, 0, m) {
			int cur = rt;
			repn(j, i + 1, m) {
				int p = t[j - 1] - 'a';
				cur = ch[cur][p];
				if (cur == 0) break;
				dp[j] = min(dp[j], dp[i] + val[cur]);
			}
		}
		if (dp[m] == INF) cout << "-1\n";
		else cout << dp[m] << "\n";
	}	
	return 0;
}