Mern Corp. sells computers and computer software to the public. Mern sold and delivered a personal computer to Whyte on credit. Whyte executed and delivered to Mern a promissory note for the purchase price and a security agreement covering the computer. If Whyte purchased the computer for personal use and Mern fails to file a financing statement, which of the following is correct?

a$.$ Perfection of Mern's security interest occurred at the time of attachment.

b$.$ The computer was a consumer good while in Mern's possession.

c$.$ Mern's security interest is not enforceable against Whyte because Mern failed to file.

d$.$ Mern does not have a perfected security interest because it failed to file a financing statement.