Answer:
20 days.
Explanation:
Assume, 1 month = 30 days.
Options:
i. $600 per month
$600/month * 1 month/30 day
= $20 per day.
ii. $30/day.
Renting daily is equal to the monthly rent after 20 days ($30 for 20days which is $30×20 i.e $600)
That is, the renting is cheaper daily only for the first 20 days after which it is equal to the monthly rent.