Final answer:
The max number of units for Summer/Winter is 15 units and for Fall/Spring is 21 units.
Step-by-step explanation:
The answer to the question is C) Summer/Winter: 15 units, Fall/Spring: 21 units.
In the given options, the max number of units for Summer/Winter is 15 units and for Fall/Spring is 21 units.
Option C is the correct answer as it satisfies the given conditions.