Question: when bjt is in cutoff?
Answer: Whenever we observe the terminals of a BJT and see that the emitter-base junction is not at least 0.6-0.7 volts, the transistor is in the cutoff region. In cutoff, the transistor appears as an open circuit between the collector and emitter terminals. As is seen in 2, this implies Vout is equal to 10 volts.