How to set duration for a due date on a Task

As per the documentation I see we can set Task due date as an Expressions or it can be Relative.
I have a duration and I need to set the Task due date when it becomes active using the duration.
Can I know the sample CMMN on how to set due date?

Hey @anindian.sasi,

What have you tried so far? You can write an expression or an ISO 8601 Period string for the Task due date.