#include <bits/stdc++.h>
using namespace std;
#define int ll
#define fi first
#define se second
#define Mp make_pair
#define pb push_back
#define SZ(a) (int(a.size()))

typedef long long ll;
typedef double db;
typedef std::pair<int, int> pii;
typedef std::vector<int> vi;
#define log(...) fprintf(stderr, __VA_ARGS__)
std::mt19937_64 gen(std::chrono::system_clock::now().time_since_epoch().count());
ll get(ll l, ll r) { std::uniform_int_distribution<ll> dist(l, r); return dist(gen); }

const int N = 1000100;

int tr[N][26], co[N], tot;
void solve() {
    int n, k;
    cin >> n >> k;
    set<int> lens;
    vi cost(k, 1e18);
    vector<vector<pii>> G(k);
    cost[0] = 0;
    vector<string> s(n);
    for(int i = 0; i < n; i++) {
        cin >> s[i];
        lens.insert(SZ(s[i]));
    }
    string t;
    cin >> t;
    for(auto len : lens) {
        for(int x = 0; x < k; x++) {
            int y = x + len;
            int w = y / k + 1;
            y %= k;
            G[y].pb(Mp(x, w));
        }
    }
    priority_queue<pii> q;
    q.push(Mp(0, 0));
    while(SZ(q)) {
        auto [dis, x] = q.top(); q.pop();
        if(-dis != cost[x]) continue;
        for(auto [y, w] : G[x])
            if(cost[y] > cost[x] + w) {
                cost[y] = cost[x] + w;
                q.push(Mp(-cost[y], y));
            }
    }
    // for(int i = 0; i < k; i++)
    //     cout << cost[i] << ' ';
    // cout << '\n';
    tot = -1;
    auto newnode = [&]() {
        tot++;
        memset(tr[tot], 0, sizeof(tr[tot]));
        co[tot] = 1e18;
        return tot;
    };
    newnode();
    auto ins = [&](string s) {
        int nw = 0;
        for(int i = 0; i < SZ(s); i++) {
            if(!tr[nw][s[i] - 'a'])
                tr[nw][s[i] - 'a'] = newnode();
            nw = tr[nw][s[i] - 'a'];
            co[nw] = min(co[nw], 1 + (SZ(s) - i - 1) / k + cost[(SZ(s) - i - 1) % k]);
        }
    };
    for(int i = 0; i < n; i++) ins(s[i]);
    vi f(SZ(t) + 1, 1e18);
    f[0] = 0;
    for(int i = 0; i < SZ(t); i++) {
        int nw = 0;
        for(int j = i; j < SZ(t); j++) {
            if(!tr[nw][t[j] - 'a']) break;
            nw = tr[nw][t[j] - 'a'];
            f[j + 1] = min(f[j + 1], f[i] + co[nw]);
        }
    }
    // for(int i = 0; i <= SZ(t); i++)
    //     cout << f[i] << ' ';
    // cout << '\n';
    cout << (f[SZ(t)] == 1e18 ? -1 : f[SZ(t)]) << '\n';
}
signed main() {
    ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
    int _; cin >> _; for(int cas = 1; cas <= _; cas++) solve();
    cerr << "time: " << (db)clock()/CLOCKS_PER_SEC << "s\n";
    return 0;
}