20. A taxpayer, age 70 , is thinking about going back to work part-time. She knows that the wages may affect the taxability of her Social Security benefits. What is the maximum percentage of Social Security benefits that could become taxable? 50% 85% 20% 100% 21. A taxpayer who is an employee is to receive a bonus check of $8,000 in the current year. His marginal tax rate is 24%, effective tax rate is 20% and average tax rate is 22%. His increased federal income tax from the bonus is: $1,760 $1,600 $1,200 $1,920