Question: Leon and Serena like to wear sweaters and enjoy delicious food. The gains from trade between Leon and Serena are most obvious in which of the following cases? a. Leon and Serena both are very good at cooking tasty food, but neither has the necessary skills to knit a sweater. b. Leon's only skill is knitting nice sweaters, and Serena's only skill is cooking delicious food. c. Leon's cooking and knitting skills are very poor, and Serena's cooking and knitting skills are also very poor. d. Leon is very good at knitting sweaters and at cooking tasty food, but Serena's skills in both of these activities are very poor.