Version 1.3.1 of iAutoCalc has been submitted to the app store for review. It should be available again in a few days.
I want to say thanks to the kind reviewer who suggested I learn how to add. In fact the bug subtracted the down payment from the price twice so adding isn't really my problem ;-)
I'll make sure to let my QA department know they missed a bug and to work harder next time!
Joking aside, the bug is fixed and a new version will be sent to Apple for review and included into the app store shortly. I have recently cleaned up some other parts of the code and want to do some additional testing before the next release.