Ben, a single taxpayer, recently retired. This year, he recelved $18,000 of Social Security benefits and had $15,000 of modifled AGI (MAGI). What amount of Social Securily benefits must Ben include in his gross income? (The formulas for computing taxable Social Security benefits for single taxpayers are provided below, if needed.) Single Taxpayers: 1. If moditied AGI+50 percent of Social Security benefits $25,000, Soclal Security benefits are not taxable. 2. 11 $25,000$34,000, taxable Social Security benefits are the lesser of (a) 85 percent of Social Security benefits or (b) 85 percent of (modified AGI $50 percent of Soclal Security benefits $34,000), plus the lesser of (1) $4,500 or (2) 50 percent of Soclai Security benefits. a. $7,050. b. 518,000 c. $4,500. d. 50