Question 1205470
.


In English,  the word / (the term)  " brass "  means  " an alloy of copper and zinc ",

and the content/proportion of these parts in an alloy is not defined / (is not specified).



So,  in  " your alloy ",  the copper is partly in the brass and partly as a pure metal.


As a consequence,  the real content of the pure copper in  " your alloy " 

is not defined properly - - - and can not be determined.


As the problem is worded,  it does not give an opportunity to answer the question.