Pushing and Popping Registers

Here is a rule:

If a subroutine is expected to alter an S register, it must first push its value onto the stack.
Just before returning to the caller, the subroutine must pop the value from the stack back into the register.

Here is an example program fragment. Subroutine subB calls subC which uses two S registers.

subB:
         sub    $sp,$sp,4    # push $ra
         sw     $ra,($sp)

         . . . .
         li     $s0,23       # use $s0
  
         jal    subC         # call subC
         nop
 
         add    $s1,$s0,$s5  # $s0 holds 23
         . . . .
         
         lw     $ra,($sp)    # pop return address
         add    $sp,$sp,4
         jr     $ra          # return to caller
         nop

# subC might use $s0 and $s1  
#       
subC:   
        # save return address
         sub    $sp,$sp,4    # push $ra
         sw     $ra,($sp)

         # save registers on the stack
		 
         sub    $sp,$sp,4    # push $s0
         sw     $s0,($sp)
         sub    $sp,$sp,4    # push $s1
         sw     $s1,($sp)

         . . . . # statements using $s0 and $s1

         lw     ,($sp)   # pop 
         
		 # restore the saved registers
         add    $sp,$sp,4
         
         lw     ,($sp)   # pop 
         
         add    $sp,$sp,4

         lw     $ra,($sp)    # pop return address
         add    $sp,$sp,4
         jr     $ra          # return to caller
         nop

Answer:

Pushing and Popping Registers

QUESTION 5: