The impeller of a centrifugal pump has an outer diameter of $200$mm with an effective outlet area of $15,000$mm$2$ and runs at $1,600$ R$.$P$.$M$.$ The blades are backward$-$facing at $30$ to the tangent. The diameters of the suction and discharge passages are $100$mm and $80$mm respectively and the discharge is $0\mathrm{.}033$m$3/$s$.$ Pressure gauges fitted to the suction and discharge passages at the same level read $3$m vacuum and $15\mathrm{.}5$m respectively of water. Water enters the impeller without shock or whirl, and the shaft power is $8\mathrm{.}2$KW under these conditions. Determine the overall efficiency, and if there is no whirl slip, determine the manometric efficiency.