You can take the numbers you got from the lecture and previous assignments and *should* take real numbers to be able to define the bottleneck and predict the performance (otherwise you can't really see what's the bottleneck if you only use variables ;)).
As we want to see if you understood the assignment, it is not important to have the exact numbers for the bandwidth for example, rather to make reasonable and realistic assumptions and show us that you know how to apply the knowledge to these numbers.
As we want to see if you understood the assignment, it is not important to have the exact numbers for the bandwidth for example, rather to make reasonable and realistic assumptions and show us that you know how to apply the knowledge to these numbers.