The two-unit coal-fired station in Figure 2 runs steadily for a full day with each turbo-generator delivering the gross output shown. The coal consumption and its higher heating value, and the station auxiliary consumption, are marked on the figure. Determine (a) the gross heat rate of the station (in kJ/kWh), (b) the net heat rate of the station (in kJ/kWh) and (c) the net overall efficiency of the station (in %).