Comment on the availability of head-of-household filing status for 2021 in each of the following independent situations:

a. Taxpayer lives alone but maintains the household of his parents. In July 2021, the parents use their savings to purchase a new BMW for $62,000.

b. Taxpayer maintains a home in which she and her dependent father live. The father enters a nursing facility for treatment of a mental disorder.

c. Taxpayer, a single parent, maintains a home in which she and her unmarried son live. The son, age 18, earns $5,000 from a part-time job.

d. Assume the same facts as in part (c), except that the son is age 19, not 18.

e. Taxpayer is married and maintains a household in which he and his dependent stepson live.

f. Taxpayer lives alone but maintains the household where her dependent daughter lives.

g. Taxpayer maintains a household that includes an unrelated friend who qualifies as his dependent.