Creating groups and use agragate function - sql

Transact-SQL
1

HEY,

I HAVE TWO TABLES: CUSTOMERS AND USERS PER CUSTOMER

image

I NEED TO CREATE TWO CUSTOMERS GROUPS: DVIR & RON - 'CRNTER GROUP', AND DANNY & DAVID 'OTHER GROUP'.
AFTER THAT I NEED TO SUM THE NUMBER OF USERS FOR EACH GROUP.

I STARED BY USING UNION ALL AND PARTITION BY:

WITH "CUST-CTE" AS 
	(
	SELECT ROW_NUMBER() OVER (ORDER BY NAME) RN , NAME   
	FROM CUSTOMERS 
	)
SELECT 'OTHER', NAME
FROM "CUST-CTE"
WHERE RN = 1
UNION ALL
SELECT 'OTHER', NAME
FROM "CUST-CTE"
WHERE RN = 2
UNION ALL
SELECT 'CENTER', NAME
FROM "CUST-CTE"
WHERE RN = 3
UNION ALL
SELECT 'CENTER', NAME
FROM "CUST-CTE"
WHERE RN = 4

AND NOW I AM STUCK WITH THE SUM.
ANY HELP PLEASE?

3

How many users should there be in the CRNTER GROUP?