Understanding of a question The cost of producing a math assessment book is made up of three main components , overhead , type-setting and printing .
In $2009$, the overhead cost for an assessment book is $\$1200$ , the cost of type setting a page is $\$18$ and the cost of printing a book with $120$ pages is $\$1.45$.
How much will it cost to produce an assessment book with $120$ pages with $5000$ copies printed ? 
My thoughts -
Overhead cost - $\$1200$ 
Then for "Type Setting" , why do I only take $18$ multiply by the number of pages ? Why I cannot - $18 \times 120 \times 5000$ which is the number of copies ? 
I think I have an understanding issue on what is "type-setting" can I get help ? Thanks in advance ! 

In the past the term meant, literally, "setting type". That is, in printing newspapers (say) physical letters were positioned as desired in a block.  Ink was then applied to the block and if paper was pressed on it, the desired image would pass to the paper.  The expression "mind your $p's$ and $q's$" arises from this operation...the physical process results in a reflection so it was very easy for a typesetter to insert a $p$ where a $q$ was intended (or conversely).
Thus, type-setting is, essentially, a one time thing.  Once the block is set you can run off as many papers as you like.  Granted, you have to reapply ink and such, but the hard part, the physical positioning of the letters, need only be done once.
