#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0), cout.tie(0);
  int tc, n, c0, c1, h, temp, res;
  string number;
  cin >> tc;
  while (tc--) {
    res = temp = 0;
    cin >> n >> c0 >> c1 >> h;
    cin >> number;
    for (int i = 0; i < n; i++) {
      if (number[i] == '0')
        res += min(c0, c1 + h);
      else
        res += min(c1, c0 + h);
    }
    cout << res << endl;
  }
  return 0;
}
