What is the required minimum efficiency of an electrostatic

What is the required minimum efficiency of an electrostatic precipitator used as the second collector, when it is preceded by a cyclone separator having an efficiency of 80% if the desired overall efficiency is 98 %?

= As, Overall Efficiency =Electrostatic Precipitator Efficiency Cyclone/Seperator Efficiency

=> 0.98 = Electrostatic Precipitator Efficiency /0.8