$$15=3\times5$$, so $5$ dollars for each book  $$3+5=8$$, $8\times5=40$ 
Jenny paid $15$ dollars for $3$ books. How many dollars should she pay in total for the same kind of books if she bought $5$ more of them? 

(1) $$34$$ 
(2) $$37$$ 
(3) $$40$$ 
(4) $$42$$ 
(5) $$44$$ 