In real practice, you're going to mix 20 ml of Leukine with 230 ml NS to make a final volume of 250 ml of 40mcg/ml solution.
Otherwise don't be surprised to have an inspector ask if you REALLY use a tuberculin syringe in compounding. Some of these hospital programs that extend a BSA to 4 decimal places cause us a hard time when Taxol is 6mg/ml.
If the question was worded as you presented it (with the answer of 21.74) then it was poorly designed.