#include <iostream>
#include <algorithm>
using namespace std;


int main()
{
    int64_t k;
    int64_t n, x, t;
    cin >> k;
    while(k--) {
        cin >> n >> x >> t;
        int64_t zero = 0;
        int64_t ans = max(zero, n - t/x) * (t / x) + min(t/x, n) * min(t/x - 1, n - 1) / 2;
        cout << ans << endl;
    }


    return 0;
}
