A woman weighing 65 kg is given 20 mg of heavy water (D2O) intravenously. Ten minutes later a blood sample was obtained from another vein and analysis of the plasma shows 0.00005 wt % of the dye. Assume that the administered dye was evenly distributed by the end of the 10 min and that none was lost this period. What compartment does this provide information about and what is the volume?