Answer:
the rate of return on Karen investment is 10% 
Step-by-step explanation:
Given that
Bought price = P = $78500 
 Sale price = S =$850,000 
 Time priod = n = 25 years (1980 to 2005) 
 Based on the above information
The Rate of return is 
= (S ÷ P)^(1 ÷ n) - 1 
= ($850,000 ÷ $78,500)^(1 ÷ 25) - 1
= 0.099973 
= 10.00%
hence, the rate of return on Karen investment is 10% 
We simply applied the above formula