To ensure that the allocated resource budget is sufficient to cover the resource costs of the project, the project manager should estimate the costs at the work package level. This involves determining the cost of resources required for each work package based on its defined scope. Once the costs for all work packages are estimated, they should be summed up to calculate the total cost of the project. This total cost can then be compared to the allocated budget to determine if the budget is sufficient. This approach aligns with the principles of cost management and budgeting in project management, where detailed cost estimation and aggregation are essential for accurate budgeting.