'रुप्यरूप' प्रकार के सिक्कों के निर्माण में किस धातु का अधिकतम मात्रा में उपयोग किया गया 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?