Record Count in AR using to_xml Options

I’m new to Ruby & using ROR as a web service. I’m returning XML
using statement:

@persons = Person.find(:all)
render :xml => persons.to_xml()

Now, this returns xml fine without any issues. However, it does not
return the number of records. Lets say there are 2 records returned
the query as shown below:

<?xml version="1.0" encoding="UTF-8"?> Vick John

Now, I need output xml as shown below which will include count as

<?xml version="1.0" encoding="UTF-8"?> 2 Vick John

Can anyone help me out???

Thanks in Advance!