nonemployee charge was $$20$ per round.

a$.$ Tom must include $$800$ in gross income

b$.$ Tom is not required to include anything in gross income because it is a de minimis fringe benefit.

c$.$ Tom is not required to include the $$800$ in gross income because the use of the course was a gift.

d$.$ Tom is not required to include anything in gross income because this is a no$-$additional$-$cost service fringe benefit.