Brandon, age 26, is a self-employed plumber. One month ago, Brandon hired his brother, age 20, to help in the business. Brandon wants to accumulate a retirement fund and decides to adopt a Keogh plan to fund his retirement. Brandon's net earnings (after certain adjustments) are $80,000.

a. What is the maximum tax-deductible contribution Brandon can make to the Keogh plan?

b. Does Brandon have to include his brother in his Keogh plan? Explain your answer.