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

#define int long long

void work(	){
	int n,x,t;
	cin>>n>>x>>t;
	if(t>=(n-1)*x){

		cout<<(n)*(n-1)/2<<endl;
		return ;
	}
	int nn = t/x;
	int ans = (n)*nn;
	ans-=(nn+1)*nn/2;
	cout<<ans<<endl;
	return ;
}
signed main(){

	int t;
	cin>>t;
	while (t--)
	{
		work();
	}
	return 0;
	
}
