If Else Statement for PDF Form

I am unfamilar with JavaScript and need to create a calculation for a PDF form. The form is used to determine profit. There is a radio button called payroll with two values, "internal" and "external". One calculation to determine costs will need to say: if payroll equals "internal" then 1.02 else .98. This number will then insert in the costs field. The other calculation to determine markup will need to say: if payroll equals "internal" then 1.2 else 1.4. Thanks in advance for the assistance.