In polypeptide met-phe-leu, what amino acid has a free carboxyl group?

Below it the structure of said Polypeptide. It is clearly shown that the carboxylic groups of Met and Phe are utilized in forming the amide bonds, while the carboxylic group of Leu is still free.

Result:

In given polypeptide the carboxylic group of Leucine is free as shown in fig.