Ummm I don't know if I am reading this correctly or not, but you said it has been refusing to eat... maybe because your friend is trying to feed a kingsnake medium and large rats??
Now, I am no Colubrid expert, but I don't think a Kingsnake can eat large rats... I have had Eastern Kings before and they were good with adult mice and jumbo mice. Do me a favor and the snake a favor and go get the snake from your friend. Just my .02cents.
I hope you made a typo and meant to say mice. Not trying to start any trouble, just looking out for the health of the snake. I would pick it up in a heartbeat if I was closer.