six test tubes are placed in a rack. to all six tubes you add 1 ml of water. then 1 ml of serum is added to the first tube and mixed well. you then transfer 1 ml of that to the second tube and again mix well. you continue the transfer of 1 ml of mixture from one tube to each subsequent tube, finally discarding 1 ml from tube 6. what is the final dilution of serum contained in tube 6? sketch the process and show your calculations