Q. Substance X is freely filtered by the glomerulus and is not reabsorbed, nor secreted nor metabolized. If - serum x concentration = 0.020 mg/ml renal artery x concentration = 0.020 mg/ml renal vein x concentration = 0.002 mg/ml urine x concentration = 14 mg/ml urine flow = 54 ml/hr lymphatic x concentration = 0.00001 mg/ml haematocrit = 0.45The GFR is: (Solved)