Proofpoint, Inc. Notes to Consolidated Financial Statements (Continued) (dollars and share amounts in thousands, except per share amounts)
Also, as part of the share purchase agreement, the unvested restricted shares of a certain employee of ObserveIT were exchanged into the right to receive $532 of deferred cash consideration. The deferred cash consideration is presented as restricted cash on the Company’s consolidated balance sheet. The deferred cash consideration of $485 was allocated to post-combination expense and was not included in the purchase price. The deferred cash consideration is subject to forfeiture if employment terminates prior to the lapse of the restrictions, and the fair value is expensed as compensation expense over the three-year vesting period.
The Discounted Cash Flow Method was used to value the acquired developed technology, in-process research and development asset, customer relationships and order backlog. The Relief from Royalty Method was used to value the acquired trade name. Management applied significant judgment in estimating the fair values of these intangible assets, which involved the use of significant assumptions with respect to forecasted revenue, forecasted operating results and discount rates.
The following table summarizes the fair values of tangible assets acquired, liabilities assumed, intangible assets and goodwill:
*Purchased in-process research and development will be accounted for as an indefinite-lived intangible asset until the underlying project is completed or abandoned.
Meta Networks, Ltd.
On May 15, 2019 (the “Meta Networks Acquisition Date”), pursuant to the terms of the share purchase agreement, the Company acquired all shares of Meta Networks, Ltd. (“Meta Networks”), an innovator in zero trust network access.
By combining Meta Networks’ innovative zero trust network access technology with the Company’s people-centric security capabilities the Company expects to make it far simpler for enterprises to precisely control employee and contractor access to on-premises, cloud and consumer applications.
These factors, among others, contributed to a purchase price in excess of the estimated fair value of acquired net identifiable assets and, as a result, goodwill was recorded in connection with the acquisition. The results of operations and the fair values of the acquired assets and liabilities assumed have been included in the accompanying consolidated financial statements since the Meta Networks Acquisition Date.  These factors, among others, contributed to a purchase price in excess of the estimated fair value of acquired net identifiable assets and, as a result, goodwill was recorded in connection with the acquisition. The results of operations and the fair values of the acquired assets and liabilities assumed have been included in the accompanying consolidated financial statements since the Meta Networks Acquisition Date.
At the Meta Networks Acquisition Date, the consideration transferred was $104,664, net of cash acquired of $104. Of the consideration transferred, $12,500 was held in escrow to secure indemnification obligations, which has not been released as of the issuance of these consolidated financial statements. The revenue from Meta Networks was not material in 2019, and due to the continued integration of the combined businesses, it was impractical to determine the earnings.
Table:
 | Estimated | Estimated
 | Fair value | Useful Life
 |  | (in years)
Current assets | $10,603 | N/A
Fixed assets | 2,132 | N/A
Operating lease right-of-use asset | 2,669 | N/A
Other assets | 652 | N/A
Customer relationships | 15,800 | 5
Order backlog | 1,300 | 1
Core/developed technology | 35,400 | 4
Trade name | 400 | 2
In-process research and development* | 20,600 | N/A
Operating lease liabilities | (3,317) | N/A
Deferred revenue | (6,700) | N/A
Other liabilities | (5,414) | N/A
Goodwill | 144,374 | Indefinite
 | $218,499 | 


Question: Which subject has the highest estimated useful life?
Answer: Goodwill