CPT coding problem need help with please

I had a question on a work paper and the answers that I put down came up incorrect and I have not been able to find the correct answer. I was wanting help from you so I know what the correct answer is if nothing else for the future.

Question: Non-Human graft for temporary wound closure 5 cm defect scalp.
I have used CPT Codes 15420-15421, 15430-15431, 15300-15321 and some others and I am not getting what I am doing wrong. I have also used like incision and repair no luck.

Please help me on this I have been working off and on with this question and until I find out what the correct code is it will drive me crazy.

Thank you
Debbie Brown

Graft

Read the rules at the beginning of the section, perhaps you are missing the prep code such as 15004 if applicable.