This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Physiology
GFR of a diabetic person is 90 ml/min. Blood glucose is 200 mg/dl. Calculate urinary glucose excretion rate if the Tm for glucose is 150 mg/min 
Select and explain. 
A. 20 mg/min, B. 30 mg/min, C. 40 mg/min, D. 50 mg/min
B: 30 mg/min
Answer: B: 30 mg/min 
Explanation: Amount of filtered glucose = Plasma concentration of glucose X GFR = 90 ml/min X 200 mg /dl = 180 mg/min Rate of excretion of Glucose = Amount filtered - Tubular maximum Rate of excretion of Glucose = 180 mg/min -150 mg/min = 30 mg/min Ref : Ganong 25th ed/page 681