求解释比较优势.下面这个题目

求解释比较优势.下面这个题目
2.Tom and Ben are both chefs who run a takeaway food outlet.Ben can make nine pizzas and ten hamburgers per hour.If Ben wants to make more pizzas he cannot make as many hamburgers per hour.If he makes ten pizzas he can only make seven hamburgers per hour.Tom also makes hamburgers and pizzas.The opportunity cost to Tom of making each pizza is four hamburgers.
c) Who is better at making pizzas,Ben or Tom?
d) Is there a basis for trade between Ben and Tom in terms of who should make pizzas and who should make hamburgers?If so,who should produce hamburgers?