A particular engine runs for a period of time during which it is found that W = 2,000 J, Q_H = 12,000 J, T_C = 450 K, and T_H = 600 K. 

(a) Is this engine 

(i) A reversible heat engine, 

(ii) An irreversible heat engine, or 

(iii) Not possible according to the laws of thermodynamics? 

(b) If your answer to part 

(a) Is option 

(ii) Or option 

(iii), Give a new value of one of the quantities (W, Q_H, T_C, or T_H) so that we are now describing a reversible heat engine. 

(c) If your answer to part 

(a) Is option 

(i) Or 

(ii), Give a new value of one of the quantities (W, Q_H, T_C, or T_H) that would make this heat engine impossible.