A hash-related question :)

Hi again guys ...

Just got this one simple and yet twisted question.

How many grams of hashish could I obtain from approx. 500 grams of ready`to`smoke bud and leafs of White Widow or Northern Lights `juana ?
Note that I would want to sift the pot since it's cheaper than using a method such as the 'bubblebag' method.

Thanks

Umm .. just another small question: is there any difference between hash obtained from a sativa plant and hash obtained from an indica ?

thanks