#include <bits/stdc++.h>
using namespace std;
int solve(int n, int c0, int c1, int h, string s) {
  int ans = 0;
  for (auto &ch : s) {
    if (ch == '0') {
      ans += min(c0, c1 + h);
    } else {
      ans += min(c1, c0 + h);
    }
  }
  return ans;
}
int main() {
  int t;
  cin >> t;
  while (t--) {
    int n, co, c1, h;
    string s;
    cin >> n >> co >> c1 >> h;
    cin >> s;
    cout << solve(n, co, c1, h, s);
    cout << endl;
  }
}
