I called up reservations and the agent used the Fastbreak BCD JH999G and then gave me a $5 off coupon MUFZ031.

I actually had priced the Fastbreak BCD versus the AA/UA BCDs and the airline rates were lower.

So I booked my reseravtion using the AA BCD and the called up to ask a question and the agent said here's a $5 coupon and changed it to the Fastbreak BCD while keeping my original lower rental rate.