The patient has an order for 15,000 units of heparin SUBQ now. Nurse A has prepared the dose of 15,000 units of heparin. Following standard practice, Nurse A shows the multidose vial of heparin (40,000 units per mL) and the syringe with the drawn dose to Nurse B. Nurse B sets up the following proportion: 40,000 units: 1 mL:: 15,000 units: x mL What volume of heparin would Nurse B expect to see in the syringe?