1 #include <bits/stdc++.h>
 2 using namespace std;
 3 #define rep(i,a,b) for(int i=a;i<=b;++i)
 4 #define fgr(i,u) for(int i=head[u];i;i=to[i])
 5 typedef long long ll;
 6 typedef unsigned long long ull;
 7 const int maxn=1000010,inf=0x3f3f3f3f;
 8 ll ans;
 9 inline int gi() {
10     int x=0; char o; bool f=true; for(;!isdigit(o=getchar());)if(o=='-') f=false;
11     for(;isdigit(o);o=getchar()) x=(x<<1)+(x<<3)+(o&15); return f?x:~x+1;
12 }
13 template <class T> bool check_Max(T &x, const T &y) {
14     if( x < y) { x = y; return false; } return true;
15 }
16 template <class T> bool check_Min(T &x, const T &y) {
17     if( x > y) { x = y; return false; } return true;
18 }
19 int v[maxn<<1],to[maxn<<1],head[maxn],p;
20 inline void link(int a,int b) { v[++p]=b; to[p]=head[a]; head[a]=p;}
21 int rt,_Max,sigma,vis[maxn],sz[maxn];
22 inline void grt(int u,int pre) {//重心------------
23     sz[u]=1;int Mx=0;
24     fgr(i,u) if(v[i]^pre&&!vis[v[i]])
25         grt(v[i],u),sz[u]+=sz[v[i]],check_Max(Mx,sz[v[i]]);
26     check_Max(Mx,sigma-sz[u]);
27     if(!check_Min(_Max,Mx)) rt=u;
28 }
29 char S[maxn],T[maxn];
30 int Len;
31 const ull base=19260817;//--------------hash
32 ull h1[maxn],h2[maxn],bis[maxn];//------hash
33 ll F[maxn],G[maxn],sf[maxn],sg[maxn];
34 int dfs(int u,int pre,int dep,ull hs) {
35     sz[u]=1; hs=hs*base+T[u]; int tmp=1;
36     if(hs==h1[dep]) F[(dep-1)%Len+1]++, ans+=sg[Len-(dep-1)%Len];
37     if(hs==h2[dep]) G[(dep-1)%Len+1]++, ans+=sf[Len-(dep-1)%Len];
38     fgr(i,u) if(v[i]^pre&&!vis[v[i]])
39         check_Max(tmp,dfs(v[i],u,dep+1,hs)+1),sz[u]+=sz[v[i]];
40     return tmp;
41 }
42 inline void solve(int u) {
43     vis[u]=1; sg[1]=sf[1]=1;
44     int tmp=0,K=0;
45 //    printf("%d %d - \n",u,ans);// de bug
46     fgr(i,u) if(!vis[v[i]]) {
47         K=min(Len,dfs(v[i],u,2,T[u])+1); check_Max(tmp,K);
48         rep(k,1,K) sf[k]+=F[k],sg[k]+=G[k],F[k]=G[k]=0;
49     }
50     rep(i,1,tmp) sf[i]=sg[i]=0;
51     fgr(i,u) if(!vis[v[i]])
52         rt=v[i],sigma=sz[v[i]],_Max=inf,grt(v[i],u),solve(rt);
53 }
54 int Tim,n;
55 int main() {
56 #ifndef ONLINE_JUDGE
57     freopen("1a.in","r",stdin);
58 #endif
59     for(Tim=gi();Tim;--Tim) {
60         memset(head,0,sizeof(head)); memset(vis,0,sizeof(vis)); p=0;
61         ans=0;
62         n=gi(); Len=gi(); scanf("%s",T+1);
63         rep(i,2,n) {int u=gi(),v=gi();link(u,v);link(v,u);}
64         scanf("%s",S+1);
65         bis[0]=1;h1[0]=h2[0]=0;
66         rep(i,1,n) {bis[i]=bis[i-1]*base; h1[i]=h1[i-1]+bis[i-1]*S[(i-1)%Len+1]; h2[i]=h2[i-1]+bis[i-1]*S[Len-(i-1)%Len];}
67         rt=1; sigma=n; _Max=inf; grt(1,0); solve(rt);
68         printf("%lld\n",ans);
69     }
70     return 0;
71 }