An amplifier without feedback has a voltage gain of 50,input resistance os 1 KΩ & Output resistance of 2.5KΩ.The input resistance of the current-shunt negative feedback amplifier using the above amplifier with a feedback factor of 0.2 is___________?
A. 1/11KΩ
B. 1/5KΩ
C. 5KΩ
D. 11KΩ