/// Brrrr Brrrr
#pragma GCC optimize("O3")
#pragma GCC optimize ("unroll-loops")
#pragma GCC target("avx,avx2,fma")

#include "bits/stdc++.h"
using namespace std;

#define pb push_back
#define F first
#define S second
#define f(i, a, b)  for(int i = a; i < b; i++)
#define all(a)  a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define sz(x) (int)(x).size()
#define mp(x,y) make_pair(x,y)
#define popCnt(x) (__builtin_popcountll(x))
#define int ll

using ll = long long;
using ii = pair<int, int>;
using ull = unsigned long long;

const int N = 1e6+5, LG = 18, MOD = (119 << 23) + 1;
const long double PI = acos(-1);
const long double EPS = 1e-7;

const int dx[] = {0,0,1,-1};
const int dy[] = {1,-1,0,0};

vector<int> adj[N];
int n, c, par[N];

void dfs(int node, int par) {

    for(auto v : adj[node])
    if(v != par) {
        ::par[v] = node;
        dfs(v, node);
    }

}

void doWork() {

    cin >> n >> c;
    vector<int> deg(n + 1);
    f(i,1,n+1)adj[i].clear();
    for(int i = 1; i < n; i++) {
        int u, v;
        cin >> u >> v;
        adj[u].pb(v);
        adj[v].pb(u);
        deg[u]++;
        deg[v]++;
    }

    dfs(1, 1);
    vector<long double> p(n + 1), p2(n + 1);
    p[c] = 1.0;
    int m;  cin >> m;
    long double ans = 0.0;
    for(int i = 1; i <= m; i++) {
        int x;  cin >> x;
        long double prop = (p[x] + p2[par[x]]);
        ans += prop;
        p[x] -= prop;
        p2[x] += prop / deg[x];
        p[par[x]] += prop / deg[x];
    }

    cout << fixed << setprecision(5) << ans << '\n';
}
int32_t main() {
#ifdef ONLINE_JUDGE
    ios_base::sync_with_stdio(0);
    cin.tie(0);
#endif // ONLINE_JUDGE

    int t = 1;
    cin >> t;
    while (t--) {
        doWork();
    }
    return 0;
}

///Look at my code ya codeomk