Aaron, age 52, has just started a consulting company. He currently employs six people, who range in age from 22 to 31 years old. Aaron estimates the average employment period for his employees will be approximately three years and would like to implement a retirement plan that will favor older participants while including an appropriate vesting schedule. In addition, Aaron would like the employees to bear the risk of investment performance within the plan. Which of the following plans is most appropriate for Aaron's company? a. SEP plan. b. Target benefit pension plan. c. SIMPLE 401(k). d. Cash balance pension plan