N-Octane is compressed reversibly at constant temperature along the critical isotherm until the critical point is reached. The initial pressure is 1 bar. The pressure takes place in a closed system. Use the Lee-Kesler method to calculate the following:

a) What is the entropy change of n-octane? 

b) Calculate the heat that must be supplied to the system to maintain isothermal conditions. 

c) Calculate the necessary amount of work.