Exercise 6.20 Consider Code Example 6.28. For this exercise, assume factorial (n) is called with input argument n=5. (a) What value is in a0 when factorial returns to the calling function? (b) Suppose you replace the instructions at addresses 08508 and 0852C with nops. Will the program: (1) enter an infinite loop but not crash; (2) crash (cause the stack to grow or shrink beyond the dynamic data segment or the PC to jump to a location outside the program); (3) produce an incorrect value in a0 when the program returns to loop (if so, what value?); or (4) run correctly despite the deleted lines? (c) Repeat part (b) with the following instruction modifications: (1) Replace the instructions at addresses 08504 and 08528 with nops. (2) Replace the instruction at address 08518 with a nop. (3) Replace the instruction at address 08530 with a nop