navi1-4  Exercise 1: Choosing the Pronoun
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  (a) You and I are going                            oeng       (two, including you)
  (b) A friend and I are going; you are staying      moe        (two, excluding you)
  (c) All of us here, you too, are going             ayoeng     (more than three, including you)
  (d) The three of them are going                    pxefo      (trial, third person)
  (e) She is going                                   po

  your    ngeyä     (the genitive of nga)
  my      oeyä      (the genitive of oe)

Reasoning: first decide whether you, the listener, are part of "we"; then
decide how many people. Two or three people use the dual or trial prefix;
more than three use ay+. The third person uses po, with lenition (p -> f)
after the prefix: mefo (two), pxefo (three), ayfo / fo (more).