The content of the registers are R 1 = 25 H , R 2 = 30 H and R 3 = 40 H . The following machine instructions are executed:

 

It is a stack (LIFO) problem.

Initial values:

$$R_1=25H,\quad R_2=30H,\quad R_3=40H$$

Step 1: PUSH operations

We push in this order:

$$PUSH\{R_1\}$$

Stack:

$$[25H]$$

Then:

$$PUSH\{R_2\}$$

Stack:

$$[25H,\ 30H]$$

Then:

$$PUSH\{R_3\}$$

Stack:

$$[25H,\ 30H,\ 40H]$$

The last value pushed is the first value popped.

Step 2: POP operations

$$POP\{R_1\}$$

gets the top value:

$$R_1=40H$$

Then:

$$POP\{R_2\}$$

gets:

$$R_2=30H$$

Then:

$$POP\{R_3\}$$

gets:

$$R_3=25H$$

Therefore,

$$\boxed{R_1=40H,\quad R_2=30H,\quad R_3=25H}$$

Answer: (a)