K purchased all 100 shares of N Corporation in 2013 for $50,000. N Corporation adopts a plan of liquidation on January 1, 2020. On May 1, 2020, N sells its only asset, land, for $10,000 cash and an installment not with a face amount and fair market value of $90,000. On December 1, 2020, N distributes the cash and not to K. In 2021, K receives $9,000 from the installment note. How much gain must K report in 2021?

a. $0

b. $4,500

c. $9,000

d. None of the above