a
(a)
$\frac{P}{T}=$ constant
Initially $\frac{P_0}{T_0}+\frac{P_0}{T_0}=\frac{2 P_0}{T_0}$
For two containers
$\frac{P_0}{T_0}+\frac{P}{T}=\frac{2 P_0}{T_0}$
$P=\frac{2 P_0 \times T \times T_0}{T_0\left(T+T_0\right)}$
or $P=\frac{2 P_0 T}{\left(T+T_0\right)}$