How many cups of rice i can cook in the bottom and middle stack?

You can cook around 1 cup of rice in the dubbas pan that is 2" in height. The pans are all interchangeable. We also have a 3" deep pan product id 39743 and can hold 56 ox liquid -
https://www.desiclik.com/dubbas-multipurpose-inner-pot-for-pip-in-instant-pot-pr-39743.html