#include<bits/stdc++.h>
using namespace std;
typedef long long int ll;


void solve()
{
    ll n,x,t;
    cin>>n>>x>>t;
    ll p= t/x;
    //cout<<p<<" ";
    ll ans=0;
    if(p==0)
    cout<<ans;
    else
    {
            if(n-p>0)
            {
                ans  =ans + p*(n-p);
                ll l= p;
                l--;
                ans = ans + (l*(l+1))/2;
            }
            else
            {
                n--;
                ans = ans + (n*(n+1))/2;
            }
            cout<<ans;
    }
    
}

int main()
{
    ll t;
    cin>>t;
    while(t--)
    {
        solve();
        cout<<endl;
    }
    
    return 0;
}

