With input fixed, base resistance changes drive and moves the inverter output.
With input fixed, base resistance changes drive and moves the inverter output. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Sixteen ohms leaves the output near the top
Input stays 5 V while base resistance 16 ohm sets collector current 3/4 A and output 9 V, and checked state MIDDLE.
RB=16Ω⇒Vout=9V
Eight ohms pulls the output to the middle
Input stays 5 V while base resistance 8 ohm sets collector current 3/2 A and output 6 V, and checked state MIDDLE.
RB=8Ω⇒Vout=6V
Four ohms reaches the low output floor
Input stays 5 V while base resistance 4 ohm sets collector current 3 A and output 0 V, and checked state LOW.