Bret Hart, an accrual basis taxpayer, has been renting out an apartment to his friend Jim Neidhart. Neidhart, afraid that Bret would throw him out, agrees to prepay 18 months worth of rent starting on November 1, 2021. The total amount of prepaid rent Bret receives is $10,000 ($500 per month). How much of the prepaid rent must Bret recognize as income on his 2021 tax return