Generate final cost using calculation on the form

Hello! 

I was wondering if there was a way to do the following:

User chooses Option A from a dropdown menu. Then the user selects quantity. From here, the form auto calculates the final "cost" for Option A times Quantity. For each Option there are 2 variables: the original price for Option A, and the % off. 

Please advise how to best go about this. 

Thank you. 

I am not sure if I understand your query correctly. Generally, the calculations can be performed using the Form calculation widget. Please refer to the guide below that can help you with performing calculations on the form.

https://www.jotform.com/help/259-How-to-Perform-Form-Calculation-Using-a-Widget

If you experience any issue with the calculation, please get back to us with the form that you are working so that we can assist you further.

Thank you!