This is very dependent on your specific website and ad slots and traffic.
It can be hard for a publisher to predict ad rates and CPMs upfront as rates correlate with 50-100 different factors, and are highly dependent on each publisher's unique traffic quality. Some of the most important factors include:
Historical domain performance records in the buyer's systems (DSPs - Demand-Side Platforms)
Visibility of ad placements
User engagement rates
Focusing on high viewability and strong engagement rates is important for long-term performance. Only ads that are seen have the potential to affect the site visitors' behavior.