A nurse is preparing to administer ampicillin 500 mg IM every 6 hr. Available is ampicillin 500 mg vial. The package insert instructs adding 1.8 mL of sterile water to yield ampicillin 250 mg/mL. How many mL should the nurse administer per dose? (Round the answer to the nearest whole number. Use a leading zero if it applies. Do not use a trailing zero.) ________ mL