A

#include<bits/stdc++.h>
using namespace std;

int main(){
    int t;
    cin>>t;

    while(t--){
        int n, m;
        string s;
        cin>>n>>m>>s;

        vector<int> cnt(7, m);

        for(auto e: s){
            cnt[e-'A']--;
            cnt[e-'A'] = max(0, cnt[e-'A']);
        }

        cout<<accumulate(cnt.begin(), cnt.end(),0)<<"\n";
    }
}