A nurse is preparing to administer a heparin infusion of 25,000 units in 250 mL of normal saline at a rate of 1000 units per hour for a client diagnosed with a Deep Vein Thrombosis (DVT). The client's initial activated partial thromboplastin time (aPTT) value is 35 seconds. Which laboratory result would indicate that the aPTT is at a therapeutic level?

A 30 seconds D 75 seconds C 60 seconds B 45 seconds