I have an active Quickbooks Merchant Account, and needed to setup online payments from my website through this merchant account. I have 2 products:A- A book were buyers pay a total fee ($24.95), and get free shipping and handlingB- An online premed course with two different payment options 1-Pay total amount 2-$99 registration, $250/month for 3 monthsFor the online course I would need to allow buyers to enter a discount code providing a $10 discount, that I can track to tell me how...