$12\mathrm{.}64$ Water falling from a height of $30$ meters at the rate of $57\frac{m^3}{m}in$ drives a water turbine connected to an electric generator at $120$ rpm $.$ If the total resisting torque due to friction is $1\mathrm{.}8$ kN at $30$ cm radius and the water leaves the turbine blades with a velocity of $3\mathrm{.}70\frac{m}{sec}$ find the power developed by the generator.

a$.308$ kW

b$.,289kW$

c$.275$ kW

d$.266$ kW