A rectangular copper bar 10 mm × 200 mm × 3 m carries 5000 A with resistance 2.5 × 10^{−5} Ω; one 200 mm × 3 m face is exposed, h = 25 W/m^{2}·K, ambient 20 °C. Determine (a) the volumetric heat generation (answer in kW/m^{3}) and (b) the exposed surface temperature by convection only (answer in °C).