How to create a Formula for order form please?

I've been trying to figure out how to make this work

Thank you for reaching support,

You may use our Form Calculations widget to make your calculations:

Here is the related guide: https://www.jotform.com/help/259-how-to-perform-form-calculation-using-a-widget

Gradually build out the input fields and once you're done you may create the calculations.

Here is an additional guide: https://www.jotform.com/help/2-how-to-create-your-first-web-form

Let us know if you have any further questions.

Best.