#include<iostream>
#include<cstring>
#include<algorithm>
using namespace std;
#define endl '\n'
int n, k, x, y, ans;
int a[200005];
int ne[400005], e[400005], h[200005], idx;
bool st[200005];
int pre[200005];

void add(int a, int b){
    e[idx] = b, ne[idx] = h[a], h[a] = idx ++;
}

void dfs(int u, int fa, int len){
    st[u] = false;
    if(u == y && ans == -1)ans = len;

    for(int i = h[u]; ~ i; i = ne[i]){
        int j = e[i];
        if(j == fa)continue;
        dfs(j, u, len + 1);
        pre[j] = u;
    }

}

void solve(){
    ans = -1;
    memset(h, -1, sizeof h);
    cin >> n >> k;
    cin >> x >> y;
    for(int i = 1; i <= k; ++ i)cin >> a[i];
    for(int i = 0; i < n - 1; ++ i){
        int a, b;
        cin >> a >> b;
        add(a, b);
        add(b, a);
    }
    dfs(x, -1, 0);
    int tmp = y;
    st[x] = true;
    while(tmp != x){
        st[tmp] = true;
        tmp = pre[tmp];
    }

    for(int i = 1; i <= k; ++ i){
        int j = a[i];
        int res = 0;
        while(true){
            if(st[j] == false){
                res ++;
                st[j] = true;
                j = pre[j];
            }
            else break;
        }
        ans += 2 * res;
    }
    cout << ans << endl;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);

    int _;
    cin >> _;
    while(_ --){
        solve();
    }
    return 0;
}