#include <bits/stdc++.h>
#define pb emplace_back
#define fst first
#define scd second
#define mkp make_pair
#define mems(a, x) memset((a), (x), sizeof(a))

using namespace std;
typedef long long ll;
typedef double db;
typedef unsigned long long ull;
typedef long double ldb;
typedef pair<ll, ll> pii;

const int maxn = 1000100;

ll n, m, K, len[maxn], ch[maxn][26], ntot, f[maxn], g[maxn], lsh[maxn], tot, h[maxn];
char t[maxn];
string s[maxn];
bool vis[maxn];

struct node {
	ll u, d;
	node(ll a = 0, ll b = 0) : u(a), d(b) {}
};

inline bool operator < (const node &a, const node &b) {
	return a.d > b.d;
}

void solve() {
	for (int i = 0; i <= ntot; ++i) {
		f[i] = 9e18;
		for (int j = 0; j < 26; ++j) {
			ch[i][j] = 0;
		}
	}
	ntot = tot = m = 0;
	scanf("%lld%lld", &n, &K);
	for (int i = 1; i <= n; ++i) {
		cin >> s[i];
		len[i] = (ll)s[i].size();
		s[i] = ' ' + s[i] + ' ';
		lsh[++tot] = len[i];
	}
	sort(lsh + 1, lsh + tot + 1);
	tot = unique(lsh + 1, lsh + tot + 1) - lsh - 1;
	for (int i = 0; i < K; ++i) {
		g[i] = 1e18;
		vis[i] = 0;
	}
	g[0] = 0;
	priority_queue<node> pq;
	pq.emplace(0, 0);
	while (pq.size()) {
		int u = pq.top().u;
		pq.pop();
		if (vis[u]) {
			continue;
		}
		vis[u] = 1;
		for (int i = 1; i <= tot; ++i) {
			ll d = 1 + (u + lsh[i]) / K, v = (u + lsh[i]) % K;
			if (g[v] > g[u] + d) {
				g[v] = g[u] + d;
				if (!vis[v]) {
					pq.emplace(v, g[v]);
				}
			}
		}
	}
	for (int i = 1; i <= n; ++i) {
		int p = 0;
		for (int j = 1; j <= len[i]; ++j) {
			if (!ch[p][s[i][j] - 'a']) {
				ch[p][s[i][j] - 'a'] = ++ntot;
			}
			p = ch[p][s[i][j] - 'a'];
			f[p] = min(f[p], (len[i] - j) / K + ((len[i] - j) % K ? g[K - (len[i] - j) % K] + 1 : 0) + 1);
		}
	}
	scanf("%s", t + 1);
	int le = strlen(t + 1);
	h[0] = 0;
	for (int i = 1; i <= le; ++i) {
		h[i] = 1e18;
	}
	for (int i = 0; i < le; ++i) {
		int p = 0;
		for (int j = i + 1; j <= le; ++j) {
			if (!ch[p][t[j] - 'a']) {
				break;
			}
			p = ch[p][t[j] - 'a'];
			h[j] = min(h[j], h[i] + f[p]);
		}
	}
	printf("%lld\n", h[le] > 1e17 ? -1LL : h[le]);
}

int main() {
	mems(f, 0x3f);
	int T = 1;
	scanf("%d", &T);
	while (T--) {
		solve();
	}
	return 0;
}