Calculating the PI of a peptide question.

[BioNoob]

I am having trouble calculating the pi of peptide consisting multiple amino acid groups with the pH of 7.0.

The sequence is A-P-C-K-R, and the net charge I solved was +2

The pka values are
N-terminal 7.4
C- 8.3
K- 10.5
R- 12.5
C-terminal 3.6

The PI= 9.4 but I don't understand. Please help me...

[JackBean]

I think, that the pI is just average of pIs of AAs, isn't it?

pI of COOH is 3.6? I thought it's about 2...

[BioNoob]

It says that C-terminal carboxyl group for oligopeptide is 3.6

[BioNoob]

Ladies and gentlemen, I have finally solved the puzzle.