The infusion rate is 9 mL/hr.
Solution: Divide the total units of heparin by milliliters (bag size). 20,000 units/250 mL. Set up a proportion using the quotient, 80, and solve for units per hour, using the directive of 750 units: = 80 units/mL. 750 units/80 units. Divide and solve: 9.38. Round down to find the infusion rate: 9 mL/hr.