So now we know that the sound that English speakers hear as "p" can be pronounced in three different ways: regular, aspirated, and unreleased.
Let's look at those transcriptions again:
Look at the distribution of the different pronunciations across these data. The distribution is not random. That is, we can predict where each pronunciation can occur. These facts can be shown as the following:
when it occurs at the beginning of the word.
when it occurs at the end of the word.
everywhere else.
How would you transcribe the "p" sound in each of the following words?
park 
grip 
speak 