A nurse is preparing to administer cefazolin 500 mg by intermittent IV bolus over 30 min. Available is cefazolin 500 mg in 50 mL dextrose 5% in water (DSW). The drop factor of the manual IV tubing is 10 gtt/mL. The nurse should set the manual IV infusion to deliver how many gtt/min? (Round the answer to the nearest whole number. Use a leading zero if it applies. Do not use a trailing zero.)