A statement of work (SOW) is a document that defines the scope, objectives, deliverables, timeline, and costs of a project or service. It typically includes an estimate of the number of hours required to complete the engagement, as well as the roles and responsibilities of the parties involved. A SOW is often used for penetration testing projects to ensure that both the client and the vendor have a clear and mutual understanding of what is expected and how the work will be performed. A business partnership agreement (BPA), a service level agreement (SLA), and a non-disclosure agreement (NDA) are different types of contracts that may be related to a penetration testing project, but they do not include an estimate of the number of hours required to complete the engagement. Reference: CompTIA Security+ Study Guide: Exam SY0-701, 9th Edition, page 492; What to Look For in a Penetration Testing Statement of Work?