#pragma GCC optimize("-Ofast","-funroll-all-loops","-ffast-math")
#include <bits/stdc++.h>
using namespace std;
#define SZ 666666
typedef long long ll;
int T,n,k,m;
char t[20009];
ll gj[20009],d[20009];
ll good[2200999];
int ch[1200999][26],an=0;
bool vv[20009];
// string ss[1300999];
char ss[1300999];
const int maxn = 1000005;
int st[maxn], ed[maxn];
const ll inf = 1e17;
void sol() {
    an=1;
    cin>>n>>k;
    for (int i = 0; i <= k; i++)    
        gj[i] = inf, vv[i] = 0;
    int ptr = 1;
    for(int i=1;i<=n;++i) {
        scanf("%s", ss + ptr);
        int len = strlen(ss + ptr);
        st[i] = ptr;
        ed[i] = ptr + len - 1;
        int id = len % k;
        ll V=(len - len % k)/k+1;
        if(gj[id] > V) 
            gj[id] = V;
        ptr += len;
    }
    gj[0]=0;
    vector<int> v;
    for(int i=1;i<k;++i) if(gj[i]<inf) v.push_back(i);
    priority_queue<pair<ll,int>> s;
    s.push(make_pair(-gj[0],0));
    while(s.size()) {
        auto t=s.top().second; s.pop();
        if(vv[t]) continue; vv[t]=1;
        for(int j = 0; j < k; j++) {
            int z=t+j; ll v=gj[j]+gj[t];
            while (z>=k) z-=k, ++v;
            if(v>=gj[z]) continue;
            gj[z]=v; s.push(make_pair(-gj[z],z));
//            gj[z]=min(gj[z],v);
        }
    }
    memset(vv,0,sizeof vv);
    memset(ch[0], 0, sizeof(ch[0]));
    good[0] = inf;
    for(int i=1;i<=n;++i) {
        int o=1;
        for(int j=st[i];j <= ed[i];++j) {
            int c=ss[j]-'a';
            if(!ch[o][c]) {
                ch[o][c]=++an;
                good[an] = inf;
                for (int j = 0; j < 26; j++) ch[an][j] = 0;
            }
            o=ch[o][c];
            int len = ed[i] - j;
            ll t=len%k;
            ll w=1+len/k;
            if(t) w+=gj[k-t]+1;
            good[o]=min(good[o],w);
        }
    }
    scanf("%s", t+1);
    m=strlen(t+1);
    assert(m <= 5000);
    assert(m > 0);
    for (int i = 0; i <= m; i++) d[i] = inf;
    d[0]=0;
    for(int x=0;x<=m;++x) {
        int o=1;
        for(int j=x+1;j<=m;++j) {
            o=ch[o][t[j]-'a'];
            if(o) d[j]=min(d[j],d[x]+good[o]); else break;
        }
    }
    ll aa=d[m];
    if(aa>=inf / 2) aa=-1;
    cout<<aa<<"\n";
}
int main() {
    // ios::sync_with_stdio(0);
    // cin.tie(0);
    cin>>T;
    while(T--) sol();
    return 0;
}
/*

2
2 3
defgh
abc
abcde
1 1
a
b

*/