At part of budget planning.

This option is the most efficient because it uses Cost Explorer, which is a tool that allowsyou to visualize, understand, and manage your AWS costs and usage over time1. You can create a report in CostExplorer that lists AWS billed items by user, using the user name tag as a filter2. You can then download the report as a CSV file and use it for budget planning. Option A is less efficient because it uses Amazon Athena, which is a serverless interactive query service that allows you to analyze data in Amazon S3 using standard SQL3. You would need to set up an Athena table that points to your AWS Cost and Usage Report data in S3, and then run a query to generate the report. This would incur additional costs and complexity. Option C is less efficient because it uses the billing dashboard, which provides a high-level summary of your AWS costsand usage. You can access the bill details from the billing dashboard and download them via bill, but this would not list the billed items by user. You would need to use tags to group your costs by user name, which would require additional steps. Option D is less efficient because it uses AWS Budgets, which is a tool that allows you to plan your service usage, service costs, and instance reservations. You can modify a cost budget in AWS Budgets to alert with Amazon Simple Email Service (Amazon SES), but this would not generate a report of AWS billed items by user. This would only notify you when your actual or forecasted costs exceed or are expected to exceed your budgeted amount.