Table:
|  | 2019 | 2018 |
| --- | --- | --- |
| Computer hardware, at cost | $190.2 | $217.1 |
| Computer software, at cost | 66.7 | 72.6 |
| Leasehold improvements, land and buildings, at cost | 247.8 | 228.9 |
| Furniture and equipment, at cost | 67.2 | 63.4 |
| Computer software, hardware, leasehold improvements, furniture, and equipment, at cost | 571.9 | 582.0 |
| Less: Accumulated depreciation | (422.2) | (437.0) |
| Computer software, hardware, leasehold improvements, furniture, and equipment, net | $149.7 | $145.0 |
Paragraphs:
Computer Equipment, Software, Furniture, and Leasehold Improvements, Net
Computer equipment, software, and furniture are depreciated using the straight-line method over the estimated useful lives of the assets, which range from three to five years. Leasehold improvements are amortized on a straight-line basis over the shorter of their estimated useful lives or the lease term. Depreciation expense was $59.2 million in fiscal 2019, $67.6 million in fiscal 2018, and $73.1 million in fiscal 2017
Computer equipment, software, furniture, leasehold improvements and the related accumulated depreciation at January 31 were as follows:
Costs incurred for computer software developed or obtained for internal use are capitalized for application development activities, if material, and immediately expensed for preliminary project activities and post-implementation activities. These capitalized costs are amortized over the software’s expected useful life, which is generally three years.
Question:
What is the difference between the largest depreciation expense and the smallest depreciation expense?