Pro-rate calculation needed dependent on month

I have created a form with some calculations but need to discount the amount due based on the month the application is submitted.  I marked the two boxes I need help with.  The first box is named "Pro-Rated Adjustment" and the second box is named "Pro-Rated Adjustment B".  I need help writing the script for each of these boxes.  Can anyone help?

Just to recap:

1. I need a script to calculate the pro-rated adjustment (-$12.50 if submitted when TODAY (box at bottom left of form) (which represents the month by a number automatically) is September ) the -$12.50 will be multiplied by a number depending on the month  For example, if they submit the application in October, the -$12.50 will be 2*-12.50;
2. I need a script to calculate the pro-rated adjustment (-$4.17 if submitted when TODAY (box at bottom left of form) (which represents the month by a number automatically) is September) the -$4.17 will be multiplied by a number depending on the month  For example, if they submit the application in October, the -$4.17 will be 2*-4.17;