Finding Current through element that offers some resistance and only permits current in one direction
The peak current would be determined by the peak voltage (200 volts) and the resistance and, that would produce 10 amps (peak). However, I think the question might be asking about the average current flowing through the device. The device I would assume to be a perfect rectifier diode in series with 20 ohms and so the current would be a half wave rectified sine wave of peak value 20 amps. 

Theory tells us that a half wave rectified signal has an average value that is 0.318 x peak value: -