Explain briefly the significance of the "specific speed" of a centrifugal or axial-flow pump. A pump is designed to be driven at 10Hz and to operate at a maximum efficiency when delivering 0.4m/s of water against a head of 20m. Calculate the specific speed. What type of pump does this value suggest? A pump built for these operating conditions has a measured overall efficiency of 70%. The same pump is now required to deliver water at 30m head. At what speed should the pump be driven if it is to operate at maximum efficiency? What will be the new rate of delivery and the power required? (6 marks)