#include <cstdio>
#include <cstring>
#include <iostream>
using namespace std;
const int maxn=1000010;
typedef long long ll;
typedef unsigned long long ull;
int cas,n,m,cnt,tot,mn,rt;
ll ans;
int to[maxn<<1],next[maxn<<1],head[maxn],siz[maxn],vis[maxn],f[maxn],g[maxn],sf[maxn],sg[maxn];
ull h1[maxn],h2[maxn],bs[maxn];
char S[maxn],T[maxn];
void getrt(int x,int fa)
{
	siz[x]=1;
	int tmp=0,i;
	for(i=head[x];i!=-1;i=next[i])	if(!vis[to[i]]&&to[i]!=fa)
		getrt(to[i],x),siz[x]+=siz[to[i]],tmp=max(tmp,siz[to[i]]);
	tmp=max(tmp,tot-siz[x]);
	if(tmp<mn)	mn=tmp,rt=x;
}
int getdep(int x,int fa,int dep,ull hs)
{
	siz[x]=1,hs=hs*1331+S[x];
	if(h1[dep]==hs)	f[(dep-1)%m+1]++,ans+=sg[m-(dep-1)%m];
	if(h2[dep]==hs)	g[(dep-1)%m+1]++,ans+=sf[m-(dep-1)%m];
	int i,tmp=1;
	for(i=head[x];i!=-1;i=next[i])	if(!vis[to[i]]&&to[i]!=fa)
		siz[x]+=siz[to[i]],tmp=max(tmp,getdep(to[i],x,dep+1,hs)+1);
	return tmp;
}
void dfs(int x)
{
	vis[x]=1;
	int i,j,k,tmp=0;
	sf[1]=sg[1]=1;
	for(i=head[x];i!=-1;i=next[i])	if(!vis[to[i]])
	{
		k=min(m,getdep(to[i],x,2,S[x])+1),tmp=max(tmp,k);
		for(j=1;j<=k;j++)	sf[j]+=f[j],sg[j]+=g[j],f[j]=g[j]=0;
	}
	for(i=1;i<=tmp;i++)	sf[i]=sg[i]=0;
	for(i=head[x];i!=-1;i=next[i])	if(!vis[to[i]])	tot=siz[to[i]],mn=1<<30,getrt(to[i],x),dfs(rt);
}
inline int rd()
{
	int ret=0,f=1;	char gc=getchar();
	while(gc<‘0‘||gc>‘9‘)	{if(gc==‘-‘)	f=-f;	gc=getchar();}
	while(gc>=‘0‘&&gc<=‘9‘)	ret=ret*10+(gc^‘0‘),gc=getchar();
	return ret*f;
}
inline void add(int a,int b)
{
	to[cnt]=b,next[cnt]=head[a],head[a]=cnt++;
}
void work()
{
	n=rd(),m=rd(),ans=0;
	scanf("%s",S+1);
	int i,a,b;
	memset(head,-1,sizeof(head[0])*(n+1)),cnt=0,memset(vis,0,sizeof(vis[0])*(n+1));
	for(i=1;i<n;i++)	a=rd(),b=rd(),add(a,b),add(b,a);
	scanf("%s",T+1);
	for(bs[0]=1,i=1;i<=n;i++)	bs[i]=bs[i-1]*1331,h1[i]=h1[i-1]+T[(i-1)%m+1]*bs[i-1],h2[i]=h2[i-1]+T[m-(i-1)%m]*bs[i-1];
	tot=n,mn=1<<30,getrt(1,0),dfs(rt);
	printf("%lld\n",ans);
}
int main()
{
	cas=rd();
	while(cas--)	work();
	return 0;
}