A gas is stored in a cylinder at a pressure of $6\mathrm{.}0$x$10\mathrm{⁵}$ N$/$m$\text{'}$ and at a temperature of $15$deg C$.($a$)$ What will be the pressure of the gas at $45$deg C if the volume of the gas does not change? $($b$)$ what is the change of internal energy of the gas?