I'm happy to help with this.

This question is definitely not up to the standards the GMAT has established for IR 2PA questions. The two answers that are correct could go in either column, so there are two perfectly legitimate ways to state the correct answer. That is NEVER the case in a bonafide GMAT IR 2PA --- in the official questions, there is ALWAYS a meaningful difference between the columns. That's the entire point of this genre of question. This question falls very much short of that standard.

As for solving it ---- statements are (A) & (B) & (E) are simple inequalities, and statements (C) & (D) are equations, and it's not surprising that equations give you more information than do inequalities. Without doing any calculations, without even considering much of the material of the question, this is just a slam dunk. (C) & (D), in either order. The GMAT never makes things that easy, either on DS or on the IR --- it would have you compare inequalities to inequalities, or equations to equations, or it would have combined equations or inequalities with more complex conditions ---- "If she had bought one more pen, only then would she have spent more on pens than on pencils"

BTW, the prices for pencils & pens are totally unrealistic. The GMAT, as a test that prepares people for business school, usually keeps prices in problems closer to the ballpark of real world prices, and many better GMAT prep sources follow suit.

Please let me know whether there is any question on any of this.

Mike
_________________

Mike McGarry
Magoosh Test Prep