Client is asking for the approximate delivery date before even starting sprint. So, we cannot use usual velocity approach here.
The other option left is to divide user stories in tasks and assign approximate hours to tasks. Then add time buffer to it and come up with a number.
I know it's not the correct approach as even though we are estimating for fixed scope project, product backlog can change anytime to add new items.
So, need guidance on how to deal with this situation.