Before we begin answering, we need to go over the rules of multiplying polynomials.
Unlike in regular multiplication, we have to combine the like terms in the subtracting portion of the multiplication process.
Another rule is that when there are more than 1 variable in a term, we need to take the variables as two separate variables and then proceed to multiply them.
(Assuming, of course, that this is a homework assignment and not you actually buying it cuz' in real life the numbers would be different from month to month)