I must admit, before you realize that K is no greater than 2, the problem description looks intimidating.
exactly true… getting it now… easiest proof
Now I need proofs for wf<=Rl and Wo<=Ro+Rf XDD…
thanks though…
that is easy, Wf are the fathers of Rl, so wf<=Rl; Wo are the fathers of Ro and Rf, so Wo<=Ro+Rf