Oracle.. Need help with some codes....?

My question is : Write a query that produces the following for each employee:
<employee last name> earns <salary> monthly but wants <3 times salary>. Label the column Dream Salaries. (use currency format)

The output:

Dream Salaries
----------------------------------------------------------
King earns $24,000.00 monthly but wants $72,000.00.

Ma answer is :
SELECT last_name||' earns $'|| salary ||' monthly but wants $'||salary*3 AS "Dream Salaries"
FROM employees;

but i cant get the currency format.. Anyone can help???