$1.$ Although Hank is retired, he is an excellent handyman and often works part time on small projects for neighbors and friends. Last week his neighbor, Mike, offered to pay Hank $$500$ for minor repairs to his house. Hank completed the repairs in December of this year. Hank uses the cash method of accounting and is a calendar$-$year taxpayer. Compute Hank$$s gross income for this year from each of the following alternative transactions:

a$.$ Mike is could not pay in December and gave Hank a check for $500$ in January $15$