Answer:
cash          2,790 debit
    unearned revene 2,790 credit
unearned revenue 1,860 debit
      rent revenue   1,860 credit
Explanation:
The revenue from the rent is unearned as currently the firm has to provide the rent spance for three months It will be earned as time passes.
At year-end December 31th we have earned 2 months (Nov and Dec) therefore we reocgnize for that amount
2,790 x 2/3 months = 1,860 rent revenue