A U-tube having horizontal arm of length 20 cm, has uniform cross-section area = 1 cm2. It is filled with water of volume 60 cc. What volume of a liquid of density 4 g/cc should be poured from one side into the U-tube so that no water is left in the horizontal arm of the tube ?
(a) 60 cc
(b) 45 cc
(c) 50 cc
(d) 35 cc