Correct answer is A: Unity 600
Unity 600 Max Raw Capacity 3000TB

Unity 300 Max Raw Capacity 900TB
Unity 400 Max Raw Capacity 1500TB
Unity 500 Max Raw Capacity 2100TB

Correct answer is A: Unity 600
Unity 600 Max Raw Capacity 3000TB

Unity 300 Max Raw Capacity 900TB
Unity 400 Max Raw Capacity 1500TB
Unity 500 Max Raw Capacity 2100TB

Correct answer is B: Unity 400

Based on the capacity the correct answer is the Unity 400. (unity supports 3.9PB RAW and also has 48GB RAM)
If the question asked to compare using the maximum # of drives, the correct answer would be C. Unity 500.