One mole of an ideal gas expands adiabatically from an initial state $(T_A, V_0)$ to a final state $(T_f, 5 V_0)$. Another mole of the same gas expands isothermally from a different initial state $(T_B, V_0)$ to the same final state $(T_f, 5 V_0)$. The ratio of the specific heats at constant pressure and constant volume of this ideal gas is $\gamma$. What is the ratio $T_A / T_B$?

• A
  $5^{\gamma-1}$
• B
  $5^{1-\gamma}$
• C
  $5^{\gamma}$
• D
  $5^{\gamma-1}$