Table:
|  |  | December 31, | Depreciable |
| --- | --- | --- | --- |
| (dollars in millions) | 2019 | 2018 | Lives (Years) |
| Land and rights-of-way | $117.2 | $117.2 | 20 - Indefinite |
| Buildings and leasehold improvements | 315.4 | 305.2 | 5 - 40 |
| Network equipment | 4,044.6 | 3,913.3 | 2 - 50 |
| Office software, furniture, fixtures and vehicles | 229.3 | 216.3 | 2-14 |
| Construction in process | 38.9 | 47.1 | n/a |
| Gross value | 4,745.4 | 4,599.1 |  |
| Accumulated depreciation | (2,964.6) | (2,755.1) |  |
| Property, plant and equipment, net | $1,780.8 | $1,844.0 |  |
Paragraphs:
6. Property, Plant and Equipment
Property, plant and equipment is comprised of the following:
Depreciation expense on property, plant and equipment, including assets accounted for as finance leases, totaled $290.2 million in 2019, $239.6 million in 2018 and $190.4 million in 2017. The portion of depreciation expense associated with cost of providing services was 87%, 85% and 84% in 2019, 2018 and 2017, respectively. There are numerous assets included within network equipment resulting in a range of depreciable lives between 2 and 50 years, the majority of which fall within the range of 7 to 25 years
No asset impairment losses were recognized in 2019, 2018 or 2017 on property, plant and equipment.
Question:
How many years is the minimum lifespan of the land and rights-of-way?
Answer: 20