Urine Concentration & Dilution — Practice

A researcher infuses a healthy volunteer with a substance that is freely filtered, neither reabsorbed nor secreted, but is metabolised by neither the kidney nor the body. Its plasma concentration is 1 mg/mL and urine concentration is 60 mg/mL at a urine flow of 2 mL/min. The measured haematocrit is 45%. What is this person's renal plasma flow if the filtration fraction is 0.20?