[Textbook Confusion] Jason Needs a Business Law Book

[Textbook Confusion] Jason needs a business law book. He hears that Gwen has one for sale. Jason asks his girlfriend Sakura to buy it for him from Gwen if Sakura can get it for under $40. Sakura sees Gwen in the hall and asks if she will sell the book for $30, and Gwen agrees. They are between classes, and Sakura does not mention that the book is for Jason, although all the parties were on good terms, and the identity of the buyer should not have affected Sakura's agreement. Later, however, Rima agrees to give Jason her used business law book. Jason tells Sakura that he no longer wants the book. Sakura tells Gwen about the situation with Jason. Gwen replies that she does not care if Jason wants the book or not. Gwen says that she passed up a couple of opportunities to sell the book because she thought she already had it sold and that she wants her money from either Gwen or Jason - she doesn't care who pays.
-When Sakura and Gwen enter their agreement, what type of principal is Jason?

A) Disclosed
B) Undisclosed
C) Partially disclosed
D) Unidentified
E) Legally nonexistent