Final answer:
In the core process, major subsystems are determined and assigned to an iteration during the Evaluate Solutions stage, where potential designs are compared and the best fit is selected.
Step-by-step explanation:
The determination of major subsystems and their assignment to an iteration in the core process is done during the Evaluate Solutions stage. This stage involves evaluating potential designs relative to the constraints and criteria of the project. It requires a structured process to ensure that the design not only meets the requirements but is also the best solution within the given constraints. For instance, if the best design was determined to be a solar still for desalination, other design steps will be considered in light of this choice. The goal is to ensure that the selected design can progress to detailed design and prototyping, demonstrating the math and science connections integral to the engineering process.