24 cents... Those rascals up-ed the fare again

Anyway, each card you send in will get you two entries, according to the T&C.
On the other hand, although the T&C does not explicitly say that you have to put a card into the envelope, it implies it. So, you will have to buy envelops too if you don't want them to stick it to you. But you can always send those envelope with media rate. I am not sure how much it costs this time though.