// #define _GLIBCXX_DEBUG
#include "bits/stdc++.h"
#ifdef DEBUG
#include "PrettyDebug.hpp"
#else
#define debug(...) [](auto...){}(__VA_ARGS__)
#endif
#define For(i,a,b) for(int i=a;i<=b;i++)
#define Rev(i,a,b) for(int i=a;i>=b;i--)
#define Fin(file) freopen(file,"r",stdin)
#define Fout(file) freopen(file,"w",stdout)
#define assume(expr) ((!!(expr))||(exit((fprintf(stderr,"Assumption Failed: %s on Line %d\n",#expr,__LINE__),-1)),false))
#define range basic_string_view
using namespace std; typedef long long ll;
void solve(){
    int n,K; cin>>n>>K; vector<int> has(K,1e9); vector<string> s(n+1);
    For(i,1,n) cin>>s[i],has[(K-s[i].size()%K)%K]=min(has[(K-s[i].size()%K)%K],int(s[i].size())/K+1);
    vector<int> dis(K,1e9); dis[0]=0;
    For(k,1,K-1) if(has[k]!=1e9) For(_,0,1) For(i,0,K-1) dis[(i+k)%K]=min(dis[(i+k)%K],dis[i]+has[k]);
    vector<array<int,26>> son(2); vector<int> g(2);
    For(i,1,n){
        int u=1,sz=s[i].size();
        For(j,0,sz-1){
            int c=s[i][j]-'a'; if(!son[u][c]) son[u][c]=son.size(),son.push_back(array<int,26>()),g.push_back(1e9);
            u=son[u][c]; g[u]=min(g[u],1+dis[(sz-1-j)%K]+(sz-1-j)/K);
        }
    }
    string T; cin>>T; T=' '+T; int m=T.size()-1; vector<int> f(m+1,1e9); f[0]=0;
    For(i,0,m-1){
        int u=1; For(j,i+1,m){
            if(!(u=son[u][T[j]-'a'])) break;
            f[j]=min(f[j],f[i]+g[u]);
        }
    }
    debug(f);
    cout<<(f[m]==1e9?-1:f[m])<<'\n';
}
signed main(){
    atexit([](){cerr<<"Time = "<<clock()<<" ms"<<endl;});
    int T; cin>>T; while(T--) solve();
    return 0;
}

// START TYPING IF YOU DON'T KNOW WHAT TO DO
// STOP TYPING IF YOU DON'T KNOW WHAT YOU'RE DOING
// CONTINUE, NON-STOPPING, FOR CHARLIEVINNIE

// Started Coding On: October 16 Mon, 11 : 34 : 02