=== Answer === In this toy transistor-switch model, a low input leaves the transistor in cutoff (OFF) and a high input drives it into saturation (ON), so the load behaves like an on/off branch rather than a linear amplifier. case : transistor-switch low input state : cutoff / OFF high input state : saturation / ON on-state load current : 4.80 mA === Reason Why === We model an NPN low-side switch with exact millivolt and microamp arithmetic. The base current comes from (Vin - Vbe,on)/Rb when the base-emitter junction is forward biased, and the collector current is the smaller of beta * Ib and the load-limited current (Vcc - Vce,sat)/Rl. supply voltage : 5.00 V base resistor : 10000 ohms load resistor : 1000 ohms transistor beta proxy : 100 low input : Vin=0.00 V -> Ib=0.00 mA, Ic=0.00 mA, Vce=5.00 V, state=cutoff / OFF high input : Vin=5.00 V -> Ib=0.43 mA, Ic=4.80 mA, Vce=0.20 V, state=saturation / ON high-input gain limit : 43.00 mA high-input load limit : 4.80 mA === Check === low input stays in cutoff : yes high input reaches saturation : yes switching states differ : yes on-state current is load-limited : yes load voltage matches resistor drop : yes