#include<bits/stdc++.h>
 
using namespace std;
 
#define pb push_back
#define mp make_pair
 
typedef long long ll;
typedef pair<int, int> pii;
 
const int MOD = (int)1e9 + 7;
const double EPS = 1e-9;
const int INF = INT_MAX;
const long long INFLL = (long long)1e18;
const double PI = acos(-1.0);

const int N = (int)1e5 + 5;
const int P = 1 << 18;
 
int T;
 
int main() {
#ifndef ONLINE_JUDGE
	freopen("input.txt", "r", stdin);
	freopen("output.txt", "w", stdout);
#endif
	ios::sync_with_stdio(false);
	cout.setf(ios::fixed | ios::showpoint);
	cout.precision(8);	
 	
 	cin >> T;
 	while(T--){
 	 	ll n, x, t;
 	 	cin >> n >> x >> t;
 	 	ll cnt = min(n - 1, t / x);
 	 	ll ad = 0;
 	 	if(cnt > 1) ad = max((cnt - 1) * cnt / 2, 1LL * 0);
 	 	cout << cnt * max(0 * 1LL, n - cnt) + ad << endl;
 	}

 	return 0;
}