Final answer:
Mark's financial planner recommended a 401(k) plan, which is an employer-contributed, tax-deferred, and portable retirement savings plan that allows employees to exclude union members with their own plans.
Step-by-step explanation:
The retirement plan recommended by Mark's financial planner seems to be a 401(k) plan. This type of plan involves employer contributions to an employee's retirement account on a regular basis, which the employee can also contribute to. These funds can be invested in various investment vehicles. 401(k)s are defined contribution plans, which are tax-deferred and portable between employers, ensuring that employees can take their retirement savings with them when they change jobs. Unlike traditional pension plans, they aim to protect retirees from inflation costs, and contributions can be made in such a way to exclude certain employees, like union members with their own plans, matching the criteria given in the question.