Sahrye has brought in an assortment of shoes to determine which work better for her in pumping the Inflation Lab's pedals. She begins with a pair of black ballet flats, then tries an unusual pair of see-through high-heel pumps. She then tries a pair of tan flat-heeled thong sandals, a pair of brown high-heel sandals, a pair of nearly flat-heeled flip-flips, and finally, a pink pair of flat-heeled thong sandals. Which do you think work better?