A test on a fan running at 1000 r.p.m gave the characteristics shown below. The fan has a two-speed motor so it can also run at 1500 r.p.m. The fan is used for air flow in a duct which has a resistance of 38.1 mm of water at a flow rate of 1.42 m/s. For some process a filter is used which has a resistance of 12.7 mm of water at a flow rate of 1.42 m/s and in this case the fan is run at the higher speed. 3.0 Volume flow rate (m/s) 0.5 1.0 1.5 2.0 2.5 46 52 53 48 37 19 Power consumption (kW) 0.80 1.10 1.40 1.70 Pressure (mm water) 2.05 2.60 Calculate: a. the volume rate of air delivered when the filter is fitted b. the power required under this conditions C. the fan efficiency at the operating point d. the resistance required to be put in series with the system to reduce the flow rate by 0.47 m /s