(c) $\alpha = 0.8 \Rightarrow \beta = \frac{0.8}{(1 - 0.8)} = 4$ Also $\beta = \frac{\mathrm{\Delta}i_{c}}{\mathrm{\Delta}i_{b}} \Rightarrow \mathrm{\Delta}i_{c} = \beta \times \mathrm{\Delta}i_{b} = 4 \times 6 = 24mA$
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.