Assuming that the impeller blades are vertical plates with a width about 1/5 the diameter of the impeller:
 
Agitator A    requires a 7.5 kW motor and a 76 mm diameter shaft
 
Agitator B    requires a 75 kW motor and a 127 mm diameter shaft
 
Agitator C    requires a 7.5 kW motor and a 76 mm diameter shaft


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