Final answer:
The fees should be adjusted at least 400 times a year.
Step-by-step explanation:
The retirement funds charge an administrative fee equal to 0.25% on managed assets each year. To calculate the number of times fees should be adjusted per year, we need to find the inverse of the fee rate. Since 0.25% is the same as 0.25/100 or 0.0025, we can find the inverse by dividing 1 by 0.0025, which gives us 400. So the fees should be adjusted at least 400 times a year.