A patient is to receive gentamicin as short iv infusion over a period of 1 hr. The elimination rate constant of gentamicin in this patient is 0.278 hr-1, and the volume of distribution is 14 L. If the desired maximum and minimum plasma concentration at steady state is 7 mg/L and 1 mg/L, what is the appropriate gentamicin dose administered every 8 hr as a constant rate infusion over 1 hr that will achieve the desired concentrations ?