ok here it goes. In the beginning of the piece (mm. 1-8), which is in A major by the way, we have the expository function of the piece. It is a parallel period with IAC's in measures two and six...then over to half cadences at four and eight. This part of the piece introduces the main idea.
We then shoot on over to measures 9-20. Because this part of the piece modulates to E and there is still a feeling of the same main musical idea as in the beginning I will go out on a limb and say this is the developmental function. The period is asymmetrical with the first part being 9-12 ending on a half cadence, while the second part is 8 measures long ending in a PAC. Also, notice that the material in the second section of this period is different from the first section so it is also contrasting.
Measures 21 through the end are terminative. The original key is re-established and only a I chord is present throughout the end.