Ans: C. 500 mEq(Ref Harrison 19/e p317, 12/e p368).Base deficit in question = 400 mEq.Base excess & base deficit:Refer to an excess or deficit respectively in amount of base present in blood.Total bicarbonate deficit = 0.3 x weight (kg) x base deficitBase deficit in mEq = 0.4 x weight (kg) x Total Base Deficit = (24-6) x 0.4 x 75 = 540 mEq = 500 mEq (approx.)To obtain deficit in grams, divide mEq by 12.