Exercise4:  
For this question assume that the type Card has one of four values: ♥, ♠, ♦, ♣. The initial value of Card variable is: ♠. Also assume that the Max_Length = 5;  
   
 

Operation Mystery5(updates C: Card; 
                                  updates Q: P_Queue);
      requires:  |Q| > 0;
      ensures:   there exists Pre: Str(Card) such that
                        #Q = Pre o <C> and Q = Pre o <#C>;

 
   
  Please select which test set is correct:
 

test set 1:
      inputs:         C = ♥,  Q = <♠, ♦>;
      outputs:       C = ♦,   Q = <♠, ♥>;

test set 2:
      inputs:         C = ♠,  Q = <♠, ♣>;
      outputs:       C = ♣,  Q = <♠, ♠>;

test set 3:
      inputs:         C = ♣,  Q = <♠, ♦>;
      outputs:       C = ♦,   Q = <♣, ♠ >;

test set 4:
      inputs:         C = ♦,  Q = <♠, ♦>;
      outputs:       C = ♦,  Q = <♠, ♣>


  1 and 2
2 and 3
3 and 4
none