$7.($a$)$ What four processes make up the simple ideal Rankine cycle $?$ How is Rankine cycle practically superior to the Carnot cycle as an ideal$-$power cycle?

$($b$)$ Define Coefficient of Performance $($COP$)$ and Refrigeration Capacity. What are the various factors you will keep in mind while choosing a refrigerant for vapor compression cycle?

Q$\mathrm{.}8$ derive the expression for optimum pressure ratio for the maximum network output in a Brayton cycle. What is the corresponding cycle efficiency $?$ What are the methods for improving its cycle efficiency $?$