Hi, can anyone help me walk through that computer science stack exercise:

 

1 def main(): 2 3 4 5 6 7 8 9 10 11 12 print ("in main") num = 7 x=3 y = 4 result mystery (num, x, y). # see Question 2 print ("num: " + str(num)) print ("result: " + str(result)) 13 #mystery function 14 def mystery (val, a, b): 15 16. 17 18 19 20 21 22 23 print("in mystery") # see Question 3 if (val > a): val b # Draw stack at this point in execution return val 24 main() DRAW STACK HERE 1. To the right of the program code (in the area beneath DRAW STACK HERE), draw the stack as it appears when the program reaches line 21. 2. At line 9 (marked # see Question 2), what variables are currently in scope? That is, what variables can you refer to in main on line 9 without getting a runtime error. 3. At line 17 (marked # see Question 3), what variables are currently in scope? That is, what vari- ables can you refer to in mystery on line 17 without getting a runtime error. 4. Below, give the output that would be produced by runing the whole program to completion: