#include <bits/stdc++.h>
using namespace std;
const int N = 2e5 + 5;
const int INF = 1e9;
const long long mod = 1e9 + 7;
int n, a, b, v;
string s;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int t;
  cin >> t;
  while (t--) {
    cin >> n >> a >> b >> v;
    cin >> s;
    int zero = 0, one = 0;
    for (auto isi : s) {
      if (isi == '1')
        one++;
      else
        zero++;
    }
    cout << min(zero * a + one * b, min(n * a + one * v, n * b + zero * v))
         << '\n';
  }
}
