COUNT func

Hi,
I am trying to count the number or rows in a table with similar field
values. I want to do it in one table scan.
In other words, say I want to count the number of rows in Person table,
having age equal to 40, and the number of rows with status as 'married'.
I want Person table to be scanned only once during this query.
So, basically I want to do the following:
SELECT COUNT(age=40), COUNT(status='married')
FROM Person;

I tried to use aggregate functions with group by and having clauses, but
I still can't figure it out (probably because of the lack of
experience).
Please help.
Thanks,

Oleg