Bind algorithm for Name server selection

[Bryan Giordano]

I'm trying to understand the algorithm that BIND 9.2.2 uses to figure
out which Nameserver to use when there are multiple ones returned from
a query.
Situation : 
I want the address for foo.bar.com.  I query the root DNS servers and
find out that foo.bar.com is served by ns1.bar.com and ns2.bar.com.
 
1. How does BIND decide which of the two NS servers should be queried?   
2. What if NS1 goes down?  
3. I've heard that there are weights assigned based on the number of
successful queries made to each NS.  Is this so?
4. If weights are assigned, when are they reset?  
 
 
All help is appreciated. Thanks,
-Bryan