Population data xquery - xquery

Question

For the XML data below I am trying to get the output shown here: I.e I want to see the names of the countries having a population greater than 20000 , with the conditions that the number of cities displayed should only be for those with a population more than 3500. Also, For some countries the city is within a province.
<result>
<country name="B">
<num_cities>3</num_cities>
</country>
<country name="C">
<num_cities>2</num_cities>
</country>
</result>
---------------------------This is the XML data----------------------
<country id="1" name="A" population="12000">
<name>A</name>
<city id="c1" country="1">
<name>T1</name>
<population>5000</population>
</city>
<city id="c2" country="1">
<name>T2</name>
<population>3000</population>
</city>
<city id="c3" country="1">
<name>T3</name>
<population>4000</population>
</city>
</country>
<country id="3" name="B" population="80000">
<name>B</name>
<city id="c4" country="2">
<name>T4</name>
<population>6000</population>
</city>
<city id="c5" country="2">
<name>T5</name>
<population>2000</population>
</city>
<city id="c6" country="2">
<name>T6</name>
<population>60000</population>
</city>
<city id="c7" country="2">
<name>T7</name>
<population>12000</population>
</city>
</country>
<country id="3" name="C" population="68000">
<name>C</name>
<province>P1</province>
<city id="c8" country="3">
<name>T8</name>
<population>51000</population>
</city>
<city id="c9" country="3">
<name>T9</name>
<population>3000</population>
</city>
<city id="c10" country="3">
<name>T10</name>
<population>14000</population>
</city>
</country>
I wrote this xquery but i don't know how to exclude the cities having a population > 3500. I might not have written to code correctly either...Please assist.
for $c in doc("abc")//country
let $city:= count($c/city/name)
let $citypr:= count($c/province/city/name)
where $c/#population>1000000
return
<result>
<country name='{data($c/name) }'></country>
<num_of_cities>
{
if (exists ($c/city/name)) then
$city
else
$citypr
}
</num_of_cities>
</result>

Answer 1

Some hints:
Don't bother with where clauses where you can filter down earlier, in a specifier retrieving your content.
If you want to have only one <result>, rather than one per datum, you need to start it before the FLWOR expression; whatever you 'return' will be returned once per item.
This is an example of something closer:
<result>{
for $large-country in doc("abc")//country[#population > 20000]
let $large-cities := $country/city[population > 3500]
return
<country name="{$large-country/#name}">
<num_cities>{count($large-cities)}</num_cities>
</country>
}</result>