Answer:
Between 100 and $200
Step-by-step explanation:
As we know that
Producer surplus = Market price-The actual selling rate for the products
Given information
John made as a tutor = $300
University raise it to $400
So based on this, there are various conditions like
1. John is earning $100 more as a tutor
2. If Emily enters, then the producer surplus is between $0 and $100
This price would not more than $100 because if the price is more than she has to start the tutoring when the price is $300
So overall it would lie in between $100 and $200