solely engrossed in one thing / just (one thing, no need to worry about the rest) / simply / by all means / please feel free / do not hesitate (to ask for sth)
to take care (of) / to control / to manage / to be in charge of / to look after / to run / to care about / tube / pipe / woodwind / classifier for tube-shaped objects / particle similar to 把[ba3] in 管...叫 constructions / writing brush / (coll.) to / towards