Final answer:
The contractual discount is $100 and the patient's responsibility is called coinsurance.
Step-by-step explanation:
The contractual discount in this case is $100, which is the difference between the provider's billed amount of $400 and the insurance payment of $300. The patient's responsibility of $23.56 is called coinsurance. Coinsurance is when the patient is responsible for paying a percentage of the costs after the insurance payment has been made.