Quant Daily Challenge (June 14th) | Answer Key Discussion: Hidden Constraint Flaw?

Hi everyone, while solving yesterday quant daily challenge:
A kiosk's daily revenue averaged Rs. 500 over the whole period. Removing the 10 worst-earning days, which averaged Rs. 300, raises the overall average to Rs. 520. Exactly 30 of the days earned below Rs. 500, and no day earned below Rs. 200. What is the highest possible average revenue of the days that earned at least Rs. 500?
The given answer is 600, but that's assuming the 20 days floor as 200. But since the worst days avg is 300, how come we can assume the other as 200? Correct me if I'm wrong.
Here is why I think the answer key contains a constraint flaw:
1. The Math Behind the Flawed 600 Answer:

* Total days = 110. High days (≥ 500) = 80. Low days (< 500) = 30.
* Total revenue = 110 × 500 = 55,000.
* 10 worst days total = 3,000.
* 80 high days total (assuming 600 avg) = 48,000.
* Remaining 20 low days total = 55,000 - 3,000 - 48,000 = 4,000 $\implies$ Rs. 200 each.

2. The Contradiction:
If those 20 days earned Rs. 200 each, they become strictly lower than the 10 worst days (which average Rs. 300). This completely breaks the definition of "worst days". By definition, no day outside the 10 worst days can have a value lower than the days inside that group.
3. The Real Maximum Average:
To minimize the floor for the remaining 20 days without breaking the ranking, we assume the 10 worst days are flatly Rs. 300 each. This means the lowest possible value we can give to the remaining 20 days is also Rs. 300 each, not Rs. 200.

* Minimum total for all 30 low days = 3,000 + (20 × 300) = 9,000.
* Maximum total for 80 high days = 55,000 - 9,000 = 46,000.
* True maximum average = 46,000 / 80 = Rs. 575.

Am I missing a hidden edge case here, or is the official answer key wrong? Would love to get your thoughts!