Atkin has worked for the same corporation for $36$ years. When he retires, he will receive an annual pension. The amount of his benefit will be based on the number of years he worked for the company, his age, and the history of his earnings with the company.

Atkin participates in which of the following type of employer$-$sponsored retirement plan?

$401($k$)$ plan.

$403($b$)$ plan.

Defined benefit plan.

Defined contribution plan.