#include<bits/stdc++.h>
#define ff first
#define ss second
#define pb push_back
#define ll long long
using namespace std;
typedef pair<int,int> pii;

const int mod=998244353;
inline int add(int x,int y){int ret=x+y;if(ret>=mod)ret-=mod;return ret;}
inline int sub(int x,int y){int ret=x-y;if(ret<0)ret+=mod;return ret;}
inline int mul(int x,int y){return ((ll)x*y)%mod;}
inline int step(int base,int pw){int ret=1;while(pw){if(pw&1)ret=mul(ret,base);base=mul(base,base);pw>>=1;}return ret;}
inline int invv(int x){return step(x,mod-2);}

const int maxn=1e6+10;
int inf=2e9;


const int maxalp=30;
int link[maxn],nxt[maxn][maxalp],isleaf[maxn],cnt=1,root=0;
int par[maxn],cpar[maxn],val[maxn],len[maxn];

void ins(int x,string &s,vector<int>&cost){

    int c=0;
    while(1){

        if(c==s.size()){
            return;
        }

        int sc=s[c]-'a';

        if(nxt[x][sc]==-1){
            par[cnt]=x;
            cpar[cnt]=sc;
            len[cnt]=c+1;
            nxt[x][sc]=cnt++;
        }

        x=nxt[x][sc];
        val[x]=min(val[x],cost[c]);
        c=c+1;
    }
}
int get_link(int x);
int get_nxt(int x,int c){
    if(nxt[x][c]!=-1)return nxt[x][c];
    if(x==0)return 0;
    return nxt[x][c]= get_nxt(get_link(x),c);
}
int get_link(int x){
    if(link[x]!=-1)return link[x];
    if(x==0)return -1;
    if(par[x]==0)return 0;
    return link[x]=  get_nxt(get_link(par[x]),cpar[x]);
}
void reset_aho(){


    for(int i=0;i<cnt;i++){
        link[i]=-1;
        for(int j=0;j<maxalp;j++)nxt[i][j]=-1;
        val[i]=inf;
        len[i]=-1;
    }
    cnt=1;

}


deque<int>deq[maxn];
int n,k;
string s[maxn];
int dp[maxn],tmp[maxn];
int rdp[maxn];
void upd_dp(int w,int c){

    for(int i=0;i<w;i++)deq[i].clear();

    int msum=w*c+k;

    for(int i=0;i<msum;i++)tmp[i]=inf;
    for(int i=0;i<msum;i++){

        int cid=i%w;
        while(deq[cid].size() && (i-deq[cid].front())/w>c)deq[cid].pop_front();

        int id=-1;
        if(deq[cid].size())id=deq[cid].front();

        if(id!=-1)tmp[i]=min(dp[i], dp[id]+((i-id)/w) );

        while(deq[cid].size() && dp[deq[cid].back()]+(i-deq[cid].back())/w>=dp[i] )deq[cid].pop_back();
        deq[cid].push_back(i);

    }

    /// preradi tmp
    for(int i=0;i<msum;i++)
        if(tmp[i]!=inf)
            dp[i%k]=min(dp[i%k],tmp[i]+i/k);

}

int main(){

    memset(link,-1,sizeof(link));
    memset(nxt,-1,sizeof(nxt));
    memset(len,-1,sizeof(len));
    for(int i=0;i<maxn;i++)val[i]=inf;

    ///freopen("test.txt","r",stdin);

    int t;
    scanf("%d",&t);
    while(t--){

        scanf("%d %d",&n,&k);
        vector<int>cand;
        int sum=0;
        for(int i=1;i<=n;i++){
            cin>>s[i];
            cand.pb(s[i].size());
            sum+=s[i].size();
        }
        for(int i=0;i<=sum;i++)dp[i]=inf;
        reset_aho();
        sort(cand.begin(),cand.end());
        vector<pii>cand2;

        cand2.pb({cand[0],1});
        for(int i=1;i<cand.size();i++){
            if(cand[i]==cand2.back().ff)cand2[cand2.size()-1].ss++;
            else cand2.pb({cand[i],1});
        }

        dp[0]=0;
        for(int i=0;i<cand2.size();i++)
            upd_dp(cand2[i].ff,cand2[i].ss);

        for(int i=1;i<=n;i++){
            vector<int>cost;
            for(int j=0;j<s[i].size();j++){
                int d=((int)s[i].size())-j-1;
                int cc=d/k;
                d%=k;
                if(d==0){
                    cost.pb(cc+1);
                    continue;
                }
                d=(k-d)%k;
                cost.pb(dp[d]+cc+2);
            }
            ins(root,s[i],cost);
        }

        ///printf("OPALA\n");

        string qr;
        cin>>qr;
        int curr=root;
        for(int i=1;i<=qr.size();i++)rdp[i]=inf;
        rdp[0]=0;
        for(int i=1;i<=qr.size();i++){

            curr=get_nxt(curr,qr[i-1]-'a');

            int pom=curr;
            while(pom!=root){
                rdp[i]=min(rdp[i],rdp[ i-len[pom]]+val[pom]);
                pom=get_link(pom);
            }

        }

        if(rdp[qr.size()]>=inf)printf("-1\n");
        else printf("%d\n",rdp[qr.size()]);

    }

    return 0;
}