I know the answer is 12 bushels of wheat for 19 pounds of be

I know the answer is 12 bushels of wheat for 19 pounds of beef, but I do not understand how to get that conclusion. Please explain the steps I should be taking to get this answer. Thank you!

Solution

You need to compare the opportunity cost of one country for each good in terms of other good to reach at the price at which two countries will trade with each other.