I'm sure there must be a thread or two on this, but I can't find....

I have a three day rental needed; unfortunately, it's Wednesday through Saturday at SEA, so no weekend discount and SEA's fees and taxes are usurious.

I have four free days certs: 2 of them are "Avis Free to Get Away" promo certs which says use any AWD and coupon code TUPA137. The other two are Avis Corporate Rewards Reward Day certs, and they say that they must be used with AWD U194783 and Coupon TCCA001 (that AWD makes the rate almost 50% higher than my usual AWD).

Two questions: in practice, can I combine the two kinds of certs? Second, how in the world can you actually tell when you get to the reservations page what your final cost will be, since it just says "Coupon will be applied" and you'll know what you owe when you get/checkin the car.

I'm more used to Hertz where free day coupons actually show the deducted amount on the next-to-the-last page.

Thanks!