The correct answers are four and four (4,4).
Why? Since Nettie was able to produce 8 cupcakes and 4 hamburgers within an hour, which gives her 8 cupcakes and 4 hamburgers available for trading while Becky was able to produce 4 cupcakes and 8 hamburgers in an hour. When they traded each other for a certain food its value will be equal to the opposite food, like 1 hamburger is equivalent to 1 cupcake, Nettie consumed 4 hamburgers, while Becky consumed 4 cupcakes, which is why they both consumed 4 pieces of food each after their trade.