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Algebra Difficulty 2.0 Junior Find the answer United Kingdom

A function, defined on the set of positive integers, is such that $f(xy) = f(x) + f(y)$ for all $x$ and $y$ . It is known that $f(10) = 14$ and $f(40) = 20$ . What is the value of $f(500)$ ?

(A) $29$ (B) $30$ (C) $39$ (D) $48$ (E) $50$

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