The Farringtons entered into a signed agreement to sell their real estate to the Tucsons. The price was stated in the agreement as follows: " Sum of fifty thousand dollars ($50,000). Approximately one- third down, the balance to be paid over a period of 10 years at 7% interest. This option to expire in 30 days. One hundred dollars ($100.00) to be paid at time of agreement with said amount to be applied on purchase price." Is this an enforceable agreement? Why or Why noy ?