Ames leased an apartment to Boor at $200 a month, payable the last day of each month. The term of the written lease was from January 1, 2016, through April 30, 2017. On March 15, 2016, Boor moved out, telling Ames that he disliked all the other tenants. Ames replied, "Well, you're no prize as a tenant; I probably can get more rent from someone more agreeable." Ames and Boor then had a minor physical altercation in which neither was injured. Boor sent the apartment keys to Ames by mail. Ames wrote Boor, "It will be my pleasure to hold you for every penny you owe me. I am renting the apartment on your behalf to Clay until April 30, 2017, at $175 a month." Boor had paid his rent through February 28, 2016. Clay entered the premises on April 1, 2016. How much rent, if any, may Ames recover from Boor?