a$.$

Margit, a single taxpayer earning $$130,000$ per year, defers $$10,000$ to her employer$$s Section $401($k$)$ plan.

b$.$

Joy works for a Section $501($c$)(3)$ tax$-$exempt organization, and she participates in the Section $403($b$)$ plan her employer sponsors.

c$.$

Linh is self$-$employed and contributes the maximum to a SEP IRA plan he has for himself and his employees

d$.$

Alejandro is employed full$-$time and participates in his employer$$s Section $457$ plan.