What is the maximum IRA contribution that Mr. Janson can make under each of the following assumptions?

a. He is age 20 and single. His only income item is $13,200 interest from a trust fund.

b. He is age 40 and single. His only income item is a $31,900 share of ordinary income from a partnership.

c. He is age 60 and single. His only income item is $24,200 wages from his job.

d. He is age 46 and files a joint return with his wife. His sole proprietorship generates a $7,720 loss, and his wife's salary is $43,000.

Assume the taxable year is 2018.