#include <stdio.h>
#include <algorithm>
#include <string.h>
#include <cctype>
#include <vector>
#include <queue>
#include <bitset>
#define vi vector<int>
#define pb push_back
#define mp make_pair
#define st first
#define nd second
using namespace std;
typedef long long ll;
typedef pair <int, int> Pii;
const int INF=0x3f3f3f3f;
const int cp=998244353;
inline int mod(int x){if(x>=cp) x-=cp;if(x<0) x+=cp;return x;}
inline void plust(int &x, int y){x=mod(x+y);return ;}
inline void minut(int &x, int y){x=mod(x-y);return ;}
inline int read(){
	char ch=getchar();int x=0, f=1;
	while(!isdigit(ch)){if(ch=='-') f=-1; ch=getchar();}
	while(isdigit(ch)){x=(x<<3)+(x<<1)+ch-'0';ch=getchar();}
	return x*f;
}
inline void write(int x){
    if(x<0) putchar('-'), x=-x;
    if(x>9) write(x/10);
    putchar(x%10+'0');
}
inline int ksm(int a, int b=cp-2){
	int ret=1;
	for(; b; b>>=1, a=1ll*a*a%cp)
		if(b&1) ret=1ll*ret*a%cp;
	return ret;
}
const int N=1e6+6;
const int M=5e3+5;
const ll inf=4e18;
int tot, n, K, p, len[N], R[N], tr[N][26];ll dp[M], F[N], cost[N+M];
char s[N], t[M];
int clr(int x){memset(tr[x], 0, sizeof(tr[x])), F[x]=inf;return x;}
void work(){
	n=read(), K=read();clr(tot=1);p=0;
	for(int i=1; i<=n; ++i){
		scanf("%s", s+R[i-1]+1);
		R[i]=R[i-1]+strlen(s+R[i-1]+1);
		len[++p]=R[i]-R[i-1];
	}
	sort(len+1, len+p+1);p=unique(len+1, len+p+1)-len-1;
	cost[0]=1;queue <int> Q;Q.push(0);
	for(int i=1; i<=len[p]+K; ++i) cost[i]=inf;
	while(!Q.empty()){
		int x=Q.front();Q.pop();
		//a-K=x a>=K x
		if(x+K<=len[p]+K&&cost[x+K]==inf) cost[x+K]=cost[x]+1, Q.push(x+K);
		// a+l=x   0<a=x-l<k l<x, x-k<l
		int mn=lower_bound(len+1, len+p+1, x)-len-1;
		for(int i=mn; i>=1&&x-K<len[i]; --i)
			if(cost[x-len[i]]==inf) cost[x-len[i]]=cost[x]+1, Q.push(x-len[i]);
	}
	// for(int i=1; i<=R[n]+K; ++i) printf("%d ", cost[i]);puts("");
	//  b-k<l<b
	// for(int i=0; i<=R[n]+K; ++i) printf("%d ", cost[i]);puts("");
	for(int i=1; i<=n; ++i){
		int u=1;
		for(int j=R[i-1]+1; j<=R[i]; ++j){
			int c=s[j]-'a';if(!tr[u][c]) tr[u][c]=clr(++tot);
			u=tr[u][c];F[u]=min(F[u], cost[R[i]-j]);//printf("%d\n", F[u]);
		}
	}
	scanf("%s", t+1);int m=strlen(t+1);
	dp[0]=0;
	for(int i=1; i<=m; ++i) dp[i]=inf;
	for(int i=0; i<m; ++i){
		int u=1;if(dp[i]==inf) continue;
		for(int j=i+1; j<=m; ++j){
			int c=t[j]-'a';u=tr[u][c];
			if(!u) break;dp[j]=min(dp[j], dp[i]+F[u]);
		}
	}
	if(dp[m]==inf) puts("-1");
	else printf("%lld\n", dp[m]);
}
signed main(){
	int T=read();
	while(T--) work();
	return 0;
}