Answer
$C_v = 16.25 $
$C_p = 24.56$
Work Step by Step
We know that there are 2.5 moles of $O_2$, which has an average kinetic energy of $2.5kT$. Thus, we find that its volume is:
$ V_{O_2}=2.5\times2.5\times RT=6.25RT$
We know that there are 3 moles of $Ar$, which has an average kinetic energy of $1.5kT$. Thus, we find that its volume is:
$ V_{Ar}=3\times1.5\times RT=4.5RT$
Thus, we find:
$C_v = \frac{V_t}{nT} = \frac{6.25RT+4.5RT}{5.5T} = 16.25 $
$C_p = 16.25 + 8.314 = 24.56$
