#include <bits/stdc++.h>
using namespace std;
long long solve(string str, long long c0, long long c1, long long h) {
  long long zeroes = 0, ones = 0, cost = 0;
  for (long long i = 0; i < str.length(); i++) {
    if (str[i] == '0') {
      zeroes++;
      cost += min(c0, h + c1);
    } else {
      ones++;
      cost += min(c1, h + c0);
    }
  }
  return cost;
}
int32_t main() {
  long long t;
  cin >> t;
  while (t--) {
    long long n, c0, c1, h;
    cin >> n >> c0 >> c1 >> h;
    string str;
    cin >> str;
    cout << solve(str, c0, c1, h) << endl;
  }
}
