public static HttpServletRequest listBills(HttpServletRequest request) {
        ArrayList<Models.ViewModel.Bill> viewBills = new ArrayList<>();
        ArrayList<Models.DatabaseModel.Bill> bills = Models.DatabaseModel.Bill.listBills();

        for (Models.DatabaseModel.Bill bill : bills) {
            Models.DatabaseModel.Patient patient = new Models.DatabaseModel.Patient();

            int totalCost = Models.DatabaseModel.Bill.getBillTotalCost(bill.getId());

            patient = patient.findPatient(bill.getPatientId());

            Models.ViewModel.Bill viewBill = new Models.ViewModel.Bill(bill, patient, totalCost);

            viewBills.add(viewBill);
        }
        request.setAttribute("bills", viewBills);
        request.setAttribute("view", "billlist.jsp");

        return request;
    }