Question 22

The postfix expression is: 10 5 + 60 6 / * 8 -.
We scan tokens from left to right, pushing numbers onto the stack and popping operands when an operator is encountered:

1. 10: Push onto stack $\implies [10]$
2. 5: Push onto stack $\implies [10, 5]$
3. +: Pop $5$ and $10$, compute $10 + 5 = 15$, push $15 \implies [15]$
4. 60: Push onto stack $\implies [15, 60]$
5. 6: Push onto stack $\implies [15, 60, 6]$
6. /: Pop $6$ and $60$, compute $60 / 6 = 10$, push $10 \implies [15, 10]$
7. *: Pop $10$ and $15$, compute $15 \times 10 = 150$, push $150 \implies [150]$
8. 8: Push onto stack $\implies [150, 8]$
9. -: Pop $8$ and $150$, compute $150 - 8 = 142$, push $142 \implies [142]$

The final result on top of the stack is 142 (Option C).