The specific heat of helium at constant volume is $12.6\,\text{Jmol}^{-1}\text{K}^{-1}$. The specific heat of helium at constant pressure in $\text{Jmol}^{-1}\text{K}^{-1}$ is about (Assume the temperature of the gas is moderate, universal gas constant $R = 8.314\,\text{Jmol}^{-1}\text{K}^{-1}$)