Answer:
The calculation of book value differ in case of these two equipment because of difference in time of disposal.
Explanation:
The first equipment must have been sold at the beginning of fiscal year. because at the beginning of fiscal year there is no need to subtract depreciation from the book value.
The second piece of equipment must have been sold at some time other than the beginning of fiscal year. That's why depreciation needs to be deducted from the book value.