Two identical finite bodies of constant heat capacity at temperatures T1 and T2 are available to do work in a heat engine. The final temperature Tf reached by the bodies on delivery of maximum work is

• A. \({T_F} = \frac{{{T_1} + {T_2}}}{2}\)
• B. \({T_f} = \sqrt {{T_1}{T_2}} \)
• C. Tf = T1­ = T2
• D. \({T_f} = \sqrt {T_1^2 + T_2^2} \)