some mistakes in a4 written part

Hello! Thanks for your repo!
I found in a4 written part (c), the BLEU score may be wrong.
In (i)
Regarding c1: p1=0.6, p2=0.5; c2: p1=0.8,p2=0.5. 
In (ii)
c1: p1=0.6, p2=0.5; c2: p1=0.4, p2=0.25
I have tested with nltk.translate.bleu_score.sentence_bleu.

Best
Cheng