//author @ Ayush Aggarwal
// Let's Do this shit.
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(NULL);
    ll t;
    cin>>t;
    while(t--)
    {
        map <ll,ll> mp;
        mp.clear();
        mp[0]++;
        ll sum=0,n,k,ans=0;
        cin>>n>>k;
        ll a[n];
        string str;
        cin>>str;
        for(ll i=0;i<n;i++)
        {
            a[i] = str[i] - (ll)'a' + 49;
            //cout<<a[i]<<endl;
            sum +=a[i];
            //cout<<sum<<endl;
            ans +=mp[sum-k];
            //cout<<ans<<endl;
            mp[sum]++;
        //  cout<<mp[sum]<<endl;
        }
        cout<<ans<<endl;
    }
    return 0;
}