#include <bits/stdc++.h>
using namespace std;
const long long int mod = 1000000007;
const double pi = acos(-1.0);
string str[] = {"YES", "NO"};
long long int dx[] = {1, -1, 0, 0}, dy[] = {0, 0, -1, 1};
void ans() {
  long long int n, m, a, b, c, d, e, x, y,
      mul = 1, cn = 0, cn1 = 0, cn2 = 0, sm1 = 0, sm = 0, sm2 = 0, mx = INT_MIN,
      mx1 = INT_MIN, mn = INT_MAX, mn1 = INT_MAX, i, j, k, temp;
  cin >> n >> m >> a >> b;
  string s;
  cin >> s;
  c = count(s.begin(), s.end(), '0');
  d = count(s.begin(), s.end(), '1');
  x = c * m;
  y = d * a;
  x += y;
  y = c * m + d * b + d * m;
  i = d * a + c * b + c * a;
  cout << min(x, min(y, i)) << endl;
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int z;
  cin >> z;
  while (z--) {
    ans();
  }
  return 0;
}
