#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int t;
  cin >> t;
  int a, b, p, pos;
  int i, cost, j, k, l;
  string s;
  while (t--) {
    cin >> a >> b >> p;
    cost = 0;
    cin >> s;
    pos = s.length() - 2;
    i = s.length() - 2;
    if (s[i] == 'A') {
      cost += a;
      if (cost > p) {
        cout << s.length() << endl;
        continue;
      }
    }
    if (s[i] == 'B') {
      cost += b;
      if (cost > p) {
        cout << s.length() << endl;
        continue;
      }
    }
    while (i > 0) {
      if (s[i] == s[i - 1]) {
        i--;
        pos = i;
      }
      if (s[i] != s[i - 1] && i > 0) {
        if (s[i - 1] == 'A') {
          cost += a;
        }
        if (s[i - 1] == 'B') {
          cost += b;
        }
        if (cost <= p) {
          pos = i - 1;
          i--;
        }
        if (cost > p) {
          break;
        }
      }
    }
    cout << pos + 1 << endl;
  }
  return 0;
}
