(a) What is the gauge pressure in a $25.0^{\circ} \mathrm{C}$ car tire containing 3.60 mol of gas in a 30.0 L volume? (b) What will its gauge pressure be if you add 1.00 L of gas originally at atmospheric pressure and $25.0^{\circ} \mathrm{C}$ ? Assume the temperature returns to $25.0^{\circ} \mathrm{C}$ and the volume remains constant.