Answer: See explanation
Step-by-step explanation:
a. He works for a large private firm.
In this case, he should consider 401(k) plan since he works for a large private firm.
b. He works at a university.
In this case, he should considered the 403(b) plans. The 403(b) plan, is the retirement plan for staffs of public schools and this will be suitable for him in thus scenario.
c. He owns a small firm with employees.
In thus case, the SEP and SIMPLE plans should be considered as they're both are offered by small firms that has few employees.