Federal statute and/or theories of law that are applicable

Read the hypothetical below. What are John’s potential claims if he is terminated this week?

John is a 54-year-old man with diabetes. He has worked for Telco for 20 years. Lately, he has difficulty concentrating and makes numerous mistakes. He has missed several days of work due to his diabetes. Supervisor Mark wants to fire John this week.
a) Set forth the federal statute and/or theories of law that are applicable.
b) Identify the legal issue(s) that exist and claims that may be brought based on the facts of the case.
c) Apply the facts of the case to the elements of the law/theories of law.
d) Provide an action item agenda of specific objectives you would recommend implementing in order to prevent future exposure to liability. Be specific (e.g., if training is a recommendation, describe the type of training in detail).