A physician orders GARAMYCIN 4 mg/kg/day divided into three 50 mL piggybacks to be administered q8h to a 144-pound adult. The stock strength available is GENTAMICIN 40 mg/mL in 20-mL multi-dose vials. How many mL should be added to each piggyback? O 2. 2 mL O 2. 9 mL O 6. 6 mL 0 9. 2 mL​