Answer:
The best option for both restaurants is not to clean.
Step-by-step explanation:
If they both do not clean and they can agree on not doing it, they total income for both would be $24,000 a month, if they do clean the total income would be $18,000 and if one does and the other do not, it would be $20,000 the best option for total income of both of them would be to not clean and each earn $12,000.