Explanation
To support the requirements with the minimum amount of effort, three platform security features that are required are criteria-based sharing rules, role hierarchy, and permission sets. Criteria-based sharing rules can be used to share all accounts with the custom field "Kay Customer" to all senior account managers based on a filter condition. Role hierarchy can be used to grant access to accounts that users or their subordinates own based on the ownership and role level. Permission sets can be used to grant view and edit access to the custom field that contains sensitive information to the three designated users, regardless of their user groups or profiles