When is contour farming/plowing used?

Ryan tells ty that he will give him his best pokemon card in exchange for ty's autographed baseball card. ty feels this is a fair trade. however, when ryan trades with ty, ryan gives him his second best pokemon card instead. why was this trade not beneficial for both parties? a) ryan lied about what he was giving to ty. b) ty lied about what he was giving to ryan. c) baseball cards are worth more than pokemon cards. d) pokemon cards are worth more than baseball cards.