A company rents out a business premises to a craftsman. The tenant pays the rent quarterly in advance. On 20/12 2020, payment was received for the rent for the first quarter of 2021. The quarterly rent amounts to SEK 12,000. IB 2020 on the relevant interim account amounted to SEK 10,500. The company has received rent payments from the craftsman for a total of SEK 33,000 during 2020 (reconciled 2020-12-31)

a) How does the SEK 10,500 affect the 2020 results that exist as an IB item 2020?

b) What is the company's rental income for 2020?

c) How and to what amount will the result in 2021 be affected if the lease is the only transaction that takes place in 2021?