As an employee of New England Industries, John has an opportunity to invest pre$-$tax income in an employer$-$sponsored retirement plan. His employer will contribute $50$ cents for every dollar that John contributes to this fund. This is an example of a$($n$)$:

Roth IRA.

$401($k$)$ plan.

Keogh plan.

$$ individual retirement account $($IRA$)$ plan.