Prove whether the following statements are true or false:

a$)$ In a reversible closed system process under constant entropy and pressure, the rate of production or consumption of work equals the rate of change of enthalpy of the system.

b$)$ In a reversible closed system process under constant internal energy and volume, the rate of production or consumption of work is equal to the negative product of temperature times the rate of change of entropy of the system.

c$)$ In a steady state open system process, the sum of the exchanged amounts of heat and work $($per unit flow$)$ equals the enthalpy change of the system $($per mole$).$

d$)$ Under steady flow conditions, operation of a throttling valve $($Joule $-$ Thomson throttling valve$)$ is reversible.