diff --git a/library/include/mobilisis/calculator_functions.h b/library/include/mobilisis/calculator_functions.h
index 322653a..da87279 100644
--- a/library/include/mobilisis/calculator_functions.h
+++ b/library/include/mobilisis/calculator_functions.h
@@ -55,11 +55,16 @@ private:
     PaymentMethod getPaymentMethodId(Configuration const *cfg);
     int getMinimalParkingTime(Configuration const *cfg, PaymentMethod methodId);
     int getMaximalParkingTime(Configuration const *cfg, PaymentMethod methodId);
+    uint32_t getMinimalParkingPrice(Configuration const *cfg, PaymentMethod methodId);
 
     Ticket private_GetCostFromDuration(Configuration const* cfg,
                                        QDateTime const &start,
                                        int durationMinutes,
                                        bool prepaid = false);
+    Ticket private_GetDurationFromCost(Configuration *cfg,
+                                       QDateTime const &start,
+                                       uint32_t price,
+                                       bool prepaid = false);
 
     bool checkDurationMinutes(int minParkingTime, int maxParkingTime,
                               int durationMinutes);