Oracle Database Discussions

Hello,
I need to generate an invoice for the amount of nursery sessions a given child has attended. I can get the amount of sessions using this query:

select COUNT(s.session_id), cr.child_id
from sessions s, child_register cr
where s.session_id = cr.session_id
and cr.child_id = 'C110001'
group by cr.child_id;


Which outputs:

2 C110001

I can't figure out how to multiply the result of COUNT(s.session_id) by a row in the session table called srate (which is a number, 20)

Here are my attempts:

select COUNT(s.session_id) * s.rate, cr.child_id
from sessions s, child_register cr
where s.session_id = cr.session_id
and cr.child_id = 'C110001'
group by cr.child_id;

I get an error 'Not a group by expression which makes sense

Then I tried:

select COUNT(s.session_id) * s.rate AS total, cr.child_id
from sessions s, child_register cr
where s.session_id = cr.session_id
and cr.child_id = 'C110001'
group by total;

Error 'total' not a valid identifier, Wrapping the COUNT(s.session_id) * s.rate in parentheses gives me the same error.

I'm sure it's something blatantly obvious :(

Any help very much appreciated as always,

Mike