How to disable the access to the Manage Rate Schedules and Import Commitments tasks from the cost

Summary:

I have created Project Accountant custom role and we have a requirement to disable the access to the Manage Rate Schedules and Import Commitments tasks from the cost work area. I have removed the privileges related to these tasks from the Project Cost Transaction Processing Custom Duty role but still i am able to see or access these two tasks from the cost work area. Please Suggest.

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