Exercise 13-23 (LO. 7) Compute the additional Medicare tax for the following taxpayers. If required, round your answers to the nearest dollar. a. Mario, who is single, earns wages of $440,000 in 2019. His additional Medicare tax is $ 6,380 X. b. George and Shirley are married and file a joint return in 2019. During the year, George earns wages of $138,000, and Shirley earns wages of $210,000. Their additional Medicare tax is $ 348,000 X. C. Simon has net investment income of $38,000 and MAGI of $223,000 and files as a single taxpayer. Simon's additional Medicare tax is $ 16,720 X