According to IIA guidance, which of the following factors should the auditor in charge consider when determining the resource requirements for an audit engagement?

The number, experience, and availability of audit staff as well as the nature, complexity, and time constraints of the engagement. 

The appropriateness and sufficiency of resources and the ability to coordinate with external auditors. 

The number, proficiency, experience, and availability of audit staff as well as the ability to coordinate with external auditors. 

The appropriateness and sufficiency of resources as well as the nature, complexity, and time constraints of the engagement.