Answer:
ACV=$4,500
Explanation:
We have that the actual cash value (ACV) is defined as:

Where:
actual cash value
replacement cost or purchase price of the item
expected life of the item
current life of the item
Then we have R=$6,000, C=5years, and to find the expected life of the item we can use the depreciating of the roof, then if the roof is depreciating $200 each year we just need to divide $4,000 by $200 to find the expected life of the roof:

Then the espected life of the roof is 20 years, with this result we have all the data, then:

Then the ACV is $4,500