         return model
     }
     
-    private static func factoryMinutes(
-        duration:TimeInterval) -> DPlanTravelDuration
+    private static func factoryMinutes(duration:TimeInterval) -> DPlanTravelDuration
     {
-        let minutes:TimeInterval = duration / kSecondsInMinute
+        let minutes:TimeInterval = duration / DPlanTravelDuration.Constants.secondsInMinute
+        
         let model:DPlanTravelDuration = DPlanTravelDuration(
             type:DPlanTravelDurationType.minutes,
             amount:minutes)

        return model
    }
    
    private static func factoryHours(
        duration:TimeInterval) -> DPlanTravelDuration
    {
        let hours:TimeInterval = duration / kSecondsInHour
        let model:DPlanTravelDuration = DPlanTravelDuration(
            type:DPlanTravelDurationType.hours,
            amount:hours)

        return model
    }
    
    private static func factorySeconds(duration:TimeInterval) -> DPlanTravelDuration
    {
        let model:DPlanTravelDuration = DPlanTravelDuration(
            type:DPlanTravelDurationType.seconds,
