Why do economists measure the cost or money price of thhings when oppritunity cost is what we actually are considering when we decide whether or not to purchase something

in 1897, pershing became a tactical officer at west point, and that's where he was given the nickname "black jack." pershing's first name is "john," for which "jack" is a nickname, and he was a white man who commanded black troops. hence "black jack".

the correct answer is

d) rocket launcher