Common-emitter transistor with β = 100 has base current 50 μA. Collector current:

We have I_C = β × I_B. That is I_C = 100 × 50 μA. That is I_C = 5000 μA. So I_C = 5 mA. Emitter current I_E = I_C + I_B = 5.05 mA. Current gain (amplification) is the basis of transistor amplifiers.