Determine the effects of the following on a cash basis taxpayer's gross income for 2020 and 2021. If an amount is zero, enter "O". Gross Income 2020 Gross Income 2021 a. On December 31, 2020, the taxpayer received a $1,500 check from a customer. The taxpayer did not cash the check until January 3, 2021. b. On December 31, 2020, the taxpayer received a $1,500 check from a customer. The customer asked the taxpayer not to cash the check until January 3, 2021, after the customer's salary check could be deposited. 11 111 c. On December 31, 2020, the taxpayer received a $1,500 check from a customer. The check was not received until after the bank had closed on December 31, 2020. The taxpayer did not cash the check until January 3, 2021