Below are pictured two graphs \(X,Y\) with basepoints \(x,y\) respectively and
a covering map \(f:X\to Y\) that takes edges to edges preserving labels and
orientation.

Identify \(\pi_1(Y,y)\) with the free group with basis \(\{a,b\}\) as usual.
Describe the image of \(f_\#:\pi(X,x)\to\pi_1(Y,y)\).