Query Help

Need some help on elaborating the following:

I have a table (costumers) containing cityID's and a table (cities) containing names for 300 cities.

Problem:
I would like to display a list where it could appear for each city the total number of costummers like the following example:

Cities Total Costummers

London 32
Berlin 190
Toquio 63
Lisbon 54
(...) and so on for all of the 300 cities

How may I perform this query without repeating it 300 times? (maybe a silly question, but not for a newbie)
Thanks in advance for nay help.
MP

I didn't test this but it should be close. Join on the CityID, count the number of rows grouped by CityID

select cityname, count(*) as totalCust
from cities, costumers
where cities.id = costumers.cityID
group by cities.id

Thanks so much for your help!
It did work just as you posted without any changes.
Once again thanks for the valuable help.