#include<algorithm>
#include<cstdio>
#include<cstring>
#define pii pair<int,int>
#define mk make_pair
#define ft first
#define se second
#define pb push_back
#define db double
#define ll long long
#define ull unsigned long long
#define INF 0x3f3f3f3f
#define inf 1e18
using namespace std;
namespace IO{
    #ifndef LOCAL
        #define SIZE 30000
        char in[SIZE],out[SIZE],*p1=in,*p2=in,*p3=out;
        #define getchar() (p1==p2&&(p2=(p1=in)+fread(in,1,SIZE,stdin),p1==p2)?EOF:*p1++)
        #define flush() (fwrite(p3=out,1,SIZE,stdout))
        #define putchar(ch) (p3==out+SIZE&&flush(),*p3++=(ch))
        class Flush{public:~Flush(){fwrite(out,1,p3-out,stdout);}}_;
    #endif
    template<typename type>
    inline void read(type &x){
        x=0;bool flag=0;char ch=getchar();
        while(ch<'0'||ch>'9') flag^=ch=='-',ch=getchar();
        while(ch>='0'&&ch<='9') x=(x<<1)+(x<<3)+(ch^48),ch=getchar();
        flag?x=-x:0;
    }
    template<typename type>
    inline void write(type x,char ch=0){
        x<0?x=-x,putchar('-'):0;static short Stack[50],top=0;
        do Stack[++top]=x%10,x/=10;while(x);
        while(top) putchar(Stack[top--]|48);
        if(ch) putchar(ch);
    }
}
using namespace IO;
#define M 1000005
int n,m,ini,cnt,head[M];
struct edge{
    int nxt,v;
}e[M<<1];
void add(int u,int v){
    e[++cnt]={head[u],v};
    head[u]=cnt;
}
int fa[M],deg[M];
void dfs(int u,int f){
    fa[u]=f;
    for(int i=head[u];i;i=e[i].nxt){
        int v=e[i].v;
        if(v==f) continue;
        dfs(v,u);
        deg[u]++,deg[v]++;
    }
}
db ans,dp[M],tag[M];
void solve(){
    read(n),read(ini);
    cnt=ans=0;
    for(int i=1;i<=n;i++) head[i]=deg[i]=dp[i]=tag[i]=0;
    dp[ini]=1;
    for(int i=1,u,v;i<n;i++){
        read(u),read(v);
        add(u,v),add(v,u);
    }
    dfs(1,0);
    read(m);
    for(int i=1,u;i<=m;i++){
        read(u);
        dp[u]+=tag[fa[u]],ans+=dp[u];
        dp[fa[u]]+=dp[u]/deg[u];
        tag[u]+=dp[u]/deg[u],dp[u]=0;
    }   
    printf("%.10lf\n",ans);
}
int main(){
    int T;read(T);
    while(T--) solve();
    return 0;
}