Denny law firm represents several large corporations.

Denny law firm represents several large corporations. As a senior corporate assistant, Denny always has access to information regrading the price of stock of those corporations, as well as the business deals those corporations are considering. Denny owns stock in one of the corporations that is represented by his firm. Because of his financial interest in that corporation, Denny spends most of the time doing work for that corporation while neglecting the others.

What duties did Denny violate (if any) by spending most of the time working for the client in which he owns stock?