Using the data in Problem 8, prove that both Tina and David can be made better off

Question:

Using the data in Problem 8, prove that both Tina and David can be made better off through specialization and trade.
In problem 8
Tina can produce any of the following combinations of goods X and Y: (a) 100X and 0Y, (b) 50X and 25Y, and (c) 0X and 50Y. David can produce any of the following combinations of goods X and Y: (a) 50X and 0Y, (b) 25X and 40Y, and (c) 0X and 80Y.