Which of the following formulae is wrong?

$A$ mixture of one mole of monoatomic gas and one mole of a diatomic gas (rigid) is kept at room temperature $\left(27^{\circ} C\right)$. The ratio of the specific heat of these gases at constant volume is:

The ratio of two specific heats $\frac{C_P}{C_V}$ of $CO$ is

For hydrogen gas,$C_P - C_V = a$,and for oxygen gas,$C_P - C_V = b$. The relationship between $a$ and $b$ is given by: (where $C_P$ and $C_V$ are molar specific heats at constant pressure and constant volume,respectively.)

$A$ triatomic,diatomic,and monatomic gas are supplied the same amount of heat at constant pressure. Then:

For a gas,the difference between the two specific heats is $4150 \ J \ kg^{-1} \ K^{-1}$ and the ratio of the two specific heats is $1.4$. What is the specific heat of the gas at constant volume in units of $J \ kg^{-1} \ K^{-1}$?