A pipeline of length 2400 m is used for power transmission. If 115 kW power is to be transmitted through the pipe in which water having a pressure of $500 N/cm^2$ at inlet is flowing? Find the diameter of the pipe and efficiency of transmission if pressure drop over the length of pipe is $100 N/cm^2 $.Take f = 0.026 also find diameter if pipe corresponding to maximum efficiency of transmission.