1 free point +


1.1

2p,
  -1p if they mention `empty` wrongly

1.2

7p

  1p for accept_char
  1p for accept_nothing
  1p for accept_empty
  1p for accept_concat
  1p for accept_alt
  2p for accept_star
    1p for each direction

  0.5p if about "half" of the proof is there