3. Given a fractional-linear function of the form $f(x)=\frac{a x+b}{c x+d}$, where $a, b, c$ and $d$ are distinct natural numbers from 1 to 20. What is the smallest value that $f(2)$ can take?
Write the answer in the form of a proper fraction, do not round.

Example of answer recording: $27 / 34$

Answer: $4 / 59$