Describe how you would prioritize tasks if you had multiple demands on your time by different customers or supervisors?

You attand to them on the basis of first come first serve.

The Tasks are multiple and determine the initial not easy so you must clarify the context for the client ... and tasks vary according to the circumstances and variables .. where applicable conditions to determine the priority tasks and are through pattern recognition task. 

It means orders has not raised in Time by Customers & we have to keep all customers happy. Solution is practical experience on planning n knowing your assets. Know the maximum sales of the product from customers or their needs & schedule the production.

May be big orders on single machine without job change & short orders on multiple machines with job change.

If two customers came on the same time, my first priority is to solve the problems of both the customers, but i will see to the situation, first solve the issue who takes short time and then the other... 

Tasks should always be categorized by the situation, urgency, need or priority be it from a customer or supervisor. You can buy yourself time by speaking to a customer or supervisor by letting them know when you can have the job done. You can also delegate simple tasks or least important to a fellow colleague/ team member so that you may concentrate on the most important tasks.

I've written a couple of posts on prioritising, but in this particular case I'd say do first the work of the supervisor you're most scared of.