Dear Prof. Johann,

I am a newbie in DSGE modelling. I read the model Chapter2.mod from JohannesPfeifer/DSGE_mod (Github) but I do not understand where the equation come from?

```
//6. Monetary Policy Rule, eq. (22)
R=1/betta*Pi^phi_pi+eps_m;
```

Could you please explain to me? Because I read eq.22 in Gali book, I do not know where Betta come from!