A small new impoundment hydropower scheme is being designed and it has been decided that the scheme will use a set of identical Pelton wheel turbines. The scheme needs to supply 36 MW. At each turbine the available head is 250 m, the rotational speed is 36 rad/s, turbine efficiency is 94%, and power-specific speed is to be a maximum of 0.14 rad. How many turbines will be needed