Now we've made it to the composite ternary part of the chapter so here we go.
This piece is obviously in F minor. The first four bars end with an IAC in F minor, the second four bars with an IAC in the relative major Ab and the third four bars end with a PAC in Ab. There is a progression of stability in each but I have a hard time making any of them a period. After these three four bar phrases there is two bar extension to establish the key of Ab major. The second part of the A section modulates from Ab major to Bb flat major for a PAC in the sixth measure. The next four bars are an extension of the phrase with the exact material being repeated all four times. If you don't know the key by this point, you are a complete idiot! The next phrase is four bars long and modulates again to C major. The next phrase is eight bars long and works in sequence to get from C major back to F minor. Then after this the same extenstion from the first part of the A section followed by another two measure of V and i to make sure the listener knows the key. This could be considered a continuous rounded binary piece, but this is just the menuetto, there is still the trio left.
The trio does a direct modulation into F major. The first section of the trio consists of only one phrase that is ten bars long. There is a change in melody from right hand to left hand in measure 5 but it doesn't feel like cadence until the PAC in C major. The second section goes all sorts of crazy places due to the bass line sequence up for eight straight measure and once again contains only one phrase that is 15 bars long ending on a half cadence in F minor. Then the first part is repeated again but shortened to only eight bars and ends in a PAC in F minor. If this part were alone it would be a continuous rounded binary piece.
But since these pieces are together, they combine to form a piece in composite ternary form.