Table:
| September 30, 2019: | Weighted Average Amortization Period | Cost | Accumulated Amortization | Net |
| --- | --- | --- | --- | --- |
| Completed technologies | 6.4 years | $20,341 | $7,104 | $13,237 |
| Customer relationships | 4.8 years | 17,628 | 6,701 | 10,927 |
| Trade names | 4.5 years | 618 | 377 | 241 |
| Total intangible assets |  | $38,587 | $14,182 | $24,405 |
Paragraphs:
Intangible assets
Intangible assets include the value assigned to completed technologies, customer relationships, and trade names. The estimated useful lives for all of these intangible assets, range from two to seven years. Intangible assets as of September 30, 2019 and 2018 are summarized as follows(amounts shown in thousands, except for years):
Amortization expense related to acquired intangible assets was $7.0 million, $4.0 million, and $0.6 million for fiscal years ended September 30, 2019, 2018, and 2017, respectively and is recorded in acquisition-related costs and expenses in the consolidated statements of operations.
Question:
What is the range of the estimated useful lives of the intangible assets?
Answer: two to seven years