This is an Algebra Nation question and I'm super stumped. I'm having a mental lapse and can't tell if the .8^2 is where the rock started or the constant speed, and if it's not the constant sped; I don't know how to find it from the wording in this problem.

An astronaut drops a rock into a crater on the moon. The distance, d(t), in meters, the rock travels after t seconds can be modeled by the function d(t)=.8^2 . What is the average speed, in meters per second, of the rock between 5 and 10 seconds after it was dropped?