A gap analysis is the best option for helping the company understand the extra effort required to meet the customer requirements. A gap analysis is a step-by-step process for examining the current state of a system or process and comparing it with the desired future state, and then identifying the gaps or differences between them. A gap analysis can help to determine the scope, feasibility, and priority of the changes or improvements needed to bridge the gap and achieve the desired outcomes. A gap analysis can also help to estimate the resources, time, and cost involved in implementing the changes or improvements.
A gap analysis is different from the other options listed in the question, which are not directly related to understanding the extra effort required to meet the customer requirements. A statement of work is a document that describes the scope, objectives, deliverables, and terms and conditions of a project or contract. A statement of work can help to define the expectations and responsibilities of the parties involved in the project or contract, but it does not provide a detailed analysis of the current and future states of the system or process. A baseline is a reference point or standard that is used to measure the performance or progress of a project or process. A baseline can help to track the changes or deviations from the original plan or goal, but it does not provide a comprehensive comparison of the current and future states of the system or process. A benchmark is a point of reference or criterion that is used to evaluate the quality or performance of a system or process against a best practice or industry standard. A benchmark can help to identify the strengths and weaknesses of the system or process, but it does not provide a specific assessment of the gaps or differences between the current and future states of the system or process.