This exercise has a $5$V logic output $($the Vter in Figure $1\mathrm{.}6)$ that can source up to $10$m A of current without a severe voltage drop and stand a maximum current of $20$m A$.$ If the logic terminal sources a current larger than $20$m A$,$ it would be damaged. Or$,$ if it sources a current larger than $10$m A$,$ the Vter voltage will drop to less than $4$V $.$ We should avoid this drop in many cases. However, this logic terminal has to be used to drive an electrical component with an equivalent internal resistance of $5$ ohms $($the LOAD in Figure $1\mathrm{.}6)$ and requires a current of at least $300$m A and not exceeding $500$m A to function normally. Given that we have an NPN transistor with the current gain equals $100,$ the maximum IC current is $400$m A$,$ and the barrier potential at the BE junction is VBE $=0\mathrm{.}7$V $,$ select an appropriate value for the resistor RB revealed in the given picture to make the circuit function well.

Thank you so much.