किस मौर्य शासक को 'अमित्रघात' (शत्रुओं का विनाशक) की उपाधि से जाना जाता था?

In Ancient Indian Statecraft, Kautilya's 'Rajamandala' theory primarily deals with:

The First Buddhist Council was held at ______.

Which ancient Indian text contains references indicating that population counts or census-like records were maintained in ancient India?