1. The equation of state for a perfect gas is usually represented by the van der Waals' equation when its temperature is low and its pressure is high as PRT --ap P = 1-bp = 0.001397 m/kg for where a and b are constants and a = 0.1790 Nm/kg and b nitrogen. Determine the speed of sound of nitrogen at a temperature of -40 C and a pressure of 1.8 MPa by using the a) equation of state for a perfect gas and b) van der Waals' equation of state.