#include<bits/stdc++.h>
using namespace std;
//define shortcuts
#define ll long long int
#define fo(i,a,n) for(ll i=a;i<n;i++)
#define rfo(i,a,n) for(ll i=n-1;i>=a;i--)
#define endl "\n"
#define all(a) a.begin(),a.end()
#define sz size
#define sec second
#define fir first
#define vll vector<ll>
#define pll pair<ll,ll>
#define mll map<ll,ll>
#define pb push_back
#define ite(a) for(auto &x : a)
#define read(a) ite(a) cin>>x;
#define fast ios_base::sync_with_stdio(false); cout.tie(NULL); cin.tie(NULL);
#define ri reverse_iterator
#define MOD 1000000007
//function
ll expo(ll a, ll b, ll mod) {ll res = 1; while (b > 0) {if (b & 1)res = (res * a) % mod; a = (a * a) % mod; b = b >> 1;} return res;}
void google(int t) {cout << "Case #" << t << ": ";}
vector<ll> sieve(int n) {int*arr = new int[n + 1](); vector<ll> vect; for (int i = 2; i <= n; i++)if (arr[i] == 0) {vect.push_back(i); for (int j = 2 * i; j <= n; j += i)arr[j] = 1;} return vect;}
ll mod_add(ll a, ll b, ll m) {a = a % m; b = b % m; return (((a + b) % m) + m) % m;}
ll mod_mul(ll a, ll b, ll m) {a = a % m; b = b % m; return (((a * b) % m) + m) % m;}
ll mod_sub(ll a, ll b, ll m) {a = a % m; b = b % m; return (((a - b) % m) + m) % m;}
ll ceiling(ll n,ll m) {if(n%m==0)return n/m; else return n/m+1;}
ll fact(ll n){ll res = 1;for (ll i = 2; i <= n; i++)res = res * i;return res;}
ll nCr(ll n, ll r){return fact(n) / (fact(r) * fact(n - r));}
bool isprime(ll n){for(ll i = 2; i * i <= n; i++){if(n % i == 0){return 0;}}return 1;}
//------------------------------------------------------------------------------------------------
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

void re()
{
     ll n,x,k;
     cin>>n>>x>>k;
     ll y = (k / (x));
     ll h = min(y,n-1);
     cout<<n*h-h*(h+1)/2<<endl;
}


int main()
{
     fast;
     ll t;
     cin>>t;
     while(t--)
     {
          re();
     }
}
