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(Private)Answered by david on September 09, 2015 at 05:14 PM
You can easily achieve this using the Inventory Widget.
Check it here http://widgets.jotform.com/widget/inventory
The widget have both inventory and payment option as well, so it should fits your requirement.
Here is demo jotform you can try http://form.jotformpro.com/form/41882856448974?
The full setup for that specific form is described in this thread here:
If you have any further questions, let us know and we will be happy to help.