please do not post problems from incorrect sources.
the problem you posted is obviously NOT from the GMAT PREP software—because it's a blatant rip-off of this problem, which IS from that software:
officials-at-the-united-states-mint-believe-that-t1064.html__
also, i don't know where you got that problem—but, clearly, it's from a source that just steals GMAT PREP problems and makes a handful of insignificant changes to them.
there's no point in using questions from such a source—since, clearly, the questions have no value that you couldn't get just from studying the original GMAT PREP problems. (also, if you paid money for this source and *most* of the problems are like this, you should definitely try to get your money back!)