Explanation
= According to the Agile Practice Guide, fixed-price increments are a type of contract that can be used for agile projects, where the scope and price are agreed for each increment or iteration1. This allows the customer and the vendor to have more flexibility and transparency in defining and delivering the requirements, as well as managing the risks and changes2. Therefore, the project manager should use fixed-price increments as user stories are completed, to ensure that the vendor is paid for the value delivered, and that the project manager can control the finances while delivering results. This is also consistent with the agile principle of delivering working software frequently and satisfying the customer through early and continuous delivery of valuable software3. References:
1: Agile Practice Guide, p. 48
2: Agile Practice Guide, p. 49
3: Agile Practice Guide, p. 9