#include <bits/stdc++.h>
using namespace std;
typedef long long int ll  ;
#define pb push_back 
#define mp make_pair 
#define f first 
#define s second 
void getarr(ll arr[], ll n)
{
    for (ll i=0;i<n;i++)
    cin>>arr[i];
}
void getv(vector<ll> &arr, ll n)
{
    for (ll i=0;i<n;i++)
    {
ll k;
cin>>k;
arr.push_back(k);
}
}
int main() {
    ios::sync_with_stdio(false);
    cin.tie(NULL);
    ll t;
    cin>>t;
    while (t--)
    {
       ll n,x,t;
        cin>>n>>x>>t;
        cout<<max(0LL,n-(t/x))*(t/x)+ min(n-1,(t/x)-1)* min(n,(t/x))/2<<"\n";
        //cout<< max(0,n−t/x) * (t/x)+ min(n−1,(t/x)−1)* min(n,(t/x))/2<<'\n';
    }

    return 0;
}