Let’s assume that Bill receives a message from Annie in which she offers to sell her plasma television to Bill for $1200. Bill immediately sends her a letter saying “I have always wanted one of those televisions. But, in this economic climate, my budget is very tight. Since my business (“Moving by Bill”) is really slow right now, I will send a team to help you move all of your furniture into your new home at no charge provided that you’ll sell me the television for $600.

Question

Let’s assume that Bill receives a message from Annie in which she offers to sell her plasma television to Bill for $1200. Bill immediately sends her a letter saying “I have always wanted one of those televisions. But, in this economic climate, my budget is very tight. Since my business (“Moving by Bill”) is really slow right now, I will send a team to help you move all of your furniture into your new home at no charge provided that you’ll sell me the television for $600. 
Would this transaction be subject to the law of common law contracts or to UCC contract law?