Argon gas is adiabatically compressed to half its volume. If P, V and T represent the pressure, volume and temperature of the gaseous system, respectively, at any stage, then the correct equation representing the process is

For an adiabatic process,
             ${\mathrm{PV}}^{\mathrm{Y}}$ = constant
           ${\mathrm{TV}}^{\mathrm{\gamma }-1}$ = constant
 and   ${\mathrm{T}}^{\mathrm{\gamma }}{\mathrm{P}}^{1-\mathrm{\gamma }}$= constant 
Putting, γ = 5/3 (argon being a monatomic gas), the equation becomes: 

         ${\mathrm{PV}}^{5/3}=$ constant 
         ${\mathrm{TV}}^{-2/3} =$ constant 
         ${\mathrm{T}}^{5/3} {\mathrm{P}}^{-2/3} =$ constant ⇒ ${\mathrm{TP}}^{-2/5}=$constant