A river flows toward a lake at an average velocity of 3 m/s and a volume flow rate of 500 m^{3}/s, at a location 90 m above the lake surface. Determine (a) the total mechanical energy of the river water per unit mass (in kJ/kg) and (b) the power-generation potential of the whole river at that location (in MW). Take ρ = 1000 kg/m^{3}.