Coupon's/offers in case of lta

Hello Experts,

How to derive the final travel cost in case of any individual utilize his/her credit card redemption points while making the final flight/train fare ??

Suppose the total filght cost charged by the airline is 15000.

Redemption points (cumulated out of some earlier transactions of that individual,)utilized from credit card is 1000.

Net payment from credit card is 14000.

Thanks.