Determine $($a$)$ the specific volume and $($b$)$ the density of $20$ kg of methane gas contained in a $20$ m$3$tank$.$ The gage pressure of the methane is $61\mathrm{.}2$ kPa and the methane is in thermal equilibrium with the surroundings. The temperature and the absolute pressure of the surroundings in which the tank exists are $40\backslash$deg C and $100$ kPa, respectively.