Which of the following is excluded from the gross income calculation when determining the tax base? o a.) Alimony received b.) Unemployment benefits c.) Life insurance death benefits d.) Pensions and retirement plan distributions George contributes $1,500 to his own retirement savings accounts during the year. How does this impact George's tax due? a.) George's tax due reduces as he is eligible for a nonrefundable tax credit of $1,000. b.) George's tax due increases as he is eligible for a refundable tax credit of $2,000. c.) George's tax due reduces as he is eligible for a refundable tax credit of $1,000. d.) George's tax due increases as he is eligible for a nonrefundable tax credit of $2,000