// Jack's Candy Shop
// Solution by Adel Aly

#include <algorithm>
#include <vector>
#include <queue>
#include <cstdlib>
#include <iostream>
#include <ctime>

using namespace std;

const int MAXN = 2e5 + 10;
const int MAXM = 1e6 + 10;

int cands[MAXN], qIdx[MAXN];
long long ans;
priority_queue<int> Q[MAXN];
vector<int> adj[MAXN];

void solve(int n) {
  int myIdx = n, otherIdx;
  if (adj[n].size() > 0) {
    solve(adj[n][0]);
    myIdx = qIdx[adj[n][0]];
    for (int j = 1; j < adj[n].size(); ++j) {
      solve(adj[n][j]);
      otherIdx = qIdx[adj[n][j]];
      if (Q[otherIdx].size() > Q[myIdx].size()) {
        swap(otherIdx, myIdx);
      }

      while (!Q[otherIdx].empty()) {
        Q[myIdx].push(Q[otherIdx].top());
        Q[otherIdx].pop();
      }
    }
  }
  qIdx[n] = myIdx;
  Q[myIdx].push(n);
  while ((cands[n]--) && (!Q[myIdx].empty())) {
    ans += Q[myIdx].top();
    Q[myIdx].pop();
  }
}

int main() {
  int T, N, M, A, B, p;
  cin >> T;

  for (int tt = 1; tt <= T; ++tt) {
    ans = 0;
    cin >> N >> M >> A >> B;
    memset(cands, 0, MAXN * sizeof(int));
    ans = 0;
    for (int i = 0; i < N; i++) {
      adj[i].clear();
      while (!Q[i].empty()) {
        Q[i].pop();
      }
    }
    for (int i = 1; i < N; i++) {
      cin >> p;
      adj[p].push_back(i);
    }
    for (int i = 0; i < M; i++) {
      long long x = (1LL * A * i + B) % N;
      ++cands[x];
    }
    solve(0);
    cout << "Case #" << tt << ": " << ans << endl;
  }
  return (0);
}