Given base diameter of cylinder = 21cm

Radius (r) = 21/2 = 11.5cm

Height of cylindrical part (h_{1}) =18cm

Height of conical part (h_{2}) = 9cm

Volume of tank = volume of cylinder + volume of cone

Volume of water left in tube = Volume of cylinder – Volume of hemisphere and cone

Volume of water left in tube = 616cm^{3}