Not Display The Letter Unless Count &>= 3

SELECT name = SUBSTRING(name, 1, 1),
total = COUNT(SUBSTRING(name, 1, 1))
FROM products
GROUP BY SUBSTRING(name, 1, 1)

the assignment said that,

quote:"Do not display the letter and count unless at least three product names begin with the letter."

but i got the errors when I try following.

WHERE total >= 3

quote:Msg 207, Level 16, State 1, Line 4
Invalid column name 'total'.

WHERE COUNT(SUBSTRING(name, 1, 1)) >= 3

quote:Msg 147, Level 15, State 1, Line 1
An aggregate may not appear in the WHERE clause unless it is in a subquery contained in a HAVING clause or a select list, and the column being aggregated is an outer reference.


so what should I do?