Of the ethical components contained within rest’s model of ethical behavior, which is the one typically absent where a firm turns a blind eye to the material misstatement of a client’s financial statements and also the one, arguably, most difficult to develop in new auditors? why is it difficult to develop? how specifically should public accounting firms best address this staffing challenge?

Rest's model of ethical behavior has four basic steps:

When a firm turns a blind eye to a material misstatement of a client’s financial statements, the firm is failing in their Moral Focus, they decide not to take moral action.

Moral focus is very hard to develop since it's one thing to know what we should do, and another thing to do what we should do - "Do as I say, not as I do."

Not only accounting firms, but every company should address this ethical dilemma of ethical rules being stated (and repeated over and over again) but not enforced. The best way to deal with this is through example and leadership. If the company's group leader (maybe the manager or some other employee) acts ethically, then the rest will probably follow.

answer; operating revenues;