At $P=10$MPa and $T=60C,CO2$ has the following thermodynamic derivatives.

a$)(15$ pts each$)$ You have a continuous stream of $CO2$ at the above $T$ and MPa and $T=60C).$ You adiabatically drop the pressure in a choke valve down to $P=9$MPa. What is the downstream temperature of the $CO2?($Hint: which of the above derivatives is the right one to use?$)$

b$)$ You have a continuous stream of $CO2$ at the above $T$ and and $T=60C).$ You adiabatically compress the $CO2$ to $P=11$MPa. What is the downstream temperature of the CO$2?($Same hint as a$)$