NOTE 9—PROPERTY, PLANT AND EQUIPMENT
Significant components of property, plant and equipment are as follows (in thousands):
In fiscal 2019, we entered into agreements related to the construction and leasing of two buildings on our existing corporate campus in San Diego, California. Under these agreements, a financial institution will own the buildings, and we will lease the property for a term of five years upon their completion.
In the third quarter of fiscal 2019 we sold the land and buildings comprising our separate CTS campus in San Diego. We have entered into a lease with the buyer of this campus and CTS employees will continue to occupy this separate campus until the new buildings on our corporate campus are ready for occupancy in fiscal 2021. In the third quarter of fiscal 2019 we also sold land and buildings in Orlando, Florida and we are entering a lease for new space in Orlando to accommodate our employees and operations in Orlando. In connection with the sale of these real estate campuses we received total net proceeds of $44.9 million and recognized net gains on the sales totaling $32.5 million.
As a part of our efforts to upgrade our current information systems, early in fiscal 2015 we purchased new enterprise resource planning (ERP) software and began the process of designing and configuring this software and other software applications to manage our operations.
Costs incurred in the development of internal-use software and software applications, including external direct costs of materials and services and applicable compensation costs of employees devoted to specific software development, are capitalized as computer software costs. Costs incurred outside of the application development stage, or that are types of costs that do not meet the capitalization requirements, are expensed as incurred. Amounts capitalized are included in property, plant and equipment and are amortized on a straight-line basis over the estimated useful life of the software, which ranges from three to seven years. No amortization expense is recorded until the software is ready for its intended use.
Through September 30, 2019 we have incurred costs of $138.9 million related to the purchase and development of our ERP system, including $3.1 million, $22.5 million, and $40.6 million of costs incurred during fiscal years 2019, 2018 and 2017, respectively. We have capitalized $1.6 million, $7.5 million, and $16.7 million of qualifying software development costs as internal-use software development in progress during fiscal years 2019, 2018, and 2017, respectively. We have recognized expense for $1.5 million, $15.0 million, and $23.9 million of these costs in fiscal years 2019, 2018, and 2017, respectively, for costs that did not qualify for capitalization. Amounts that were expensed in connection with the development of these systems are classified within selling, general and administrative expenses in the Consolidated Statements of Operations.
Various components of our ERP system became ready for their intended use and were placed into service at various times from fiscal 2016 through fiscal 2019. As each component became ready for its intended use, the component’s costs were transferred into completed software and we began amortizing these costs over their seven-year estimated useful life using the straight-line method. We continue to capitalize costs associated with the development of other ERP components that are not yet ready for their intended use.
Our provisions for depreciation of plant and equipment and amortization of leasehold improvements and software amounted to $22.6 million, $19.5 million and $17.8 million in 2019, 2018 and 2017, respectively. Generally, we use straight-line methods for depreciable real property over estimated useful lives ranging from 15 to 39 years or for leasehold improvements, the term of the underlying lease if shorter than the estimated useful lives. We typically use accelerated methods (declining balance) for machinery and equipment and software other than our ERP system over estimated useful lives ranging from 5 to 10 years.
Table:
 |  | September 30,
 | 2019 | 2018
Land and land improvements | $  7,348 | $  13,132
Buildings and improvements | 48,191 | 57,959
Machinery and other equipment | 107,297 | 81,727
Software | 108,526 | 84,631
Leasehold improvements | 17,064 | 11,991
Construction and internal-use software development in progress | 16,814 | 12,888
Accumulated depreciation and amortization | (160,271) | (144,782)
 | $  144,969 | $  117,546


Question: What do the costs incurred in the development of internal-use software and software applications include?
Answer: external direct costs of materials and services and applicable compensation costs of employees devoted to specific software development