TBS 3 Mr. Smith owned a small three-unit apartment building in Tiffin, Ohio. The rent on each apartment was $1,000 per month. During 2021, he received the following payments: Apt. A - Timely rent payments were made for 12 months. Apt. B - The apartment was vacant in January and February. On 3/1/21, a new tenant entered into a 1-year lease from 3/1/21 through 2/28/22. The tenant paid first and last month's rent and a security deposit of $1,500. The security deposit is to be returned at the end of the lease if the tenant lives up to the terms of the lease. The tenant timely paid the rent for the next 9 months (April through December) on the first of each month. Apt. C - In December, after timely paying the rent for 12 months of the year, the tenant came to Mr. Smith and told him that he had been transferred to a new job location in Tennessee. He asked to be released from his 2-year lease obligation, which was scheduled to expire on June 30, 2022. Mr. Smith agreed to accept 3 months' rent to cancel the lease. The tenant paid Mr. Smith $3,000 to cancel the lease in December. Assuming Mr. Smith is a cash-basis taxpayer, what amount should Mr. Smith include his 2021 gross income from the apartment building