$($a$)$ What is the temperature of a $0\mathrm{.}89$ mol ideal$-$gas sample at the isothermal curve in the diagram below?

$($b$)$ Calculate the total expansion work done by the $0\mathrm{.}89$ mol ideal gas sample in a process that follows the cyclic path $(123456)$ as indicated in the diagram above.

Conceptual thinking:

$($c$)$ Explain why the cycle in the diagram can only proceed counterclockwise, but not clockwise.

$($d$)$ The cartoon below represents an experimental setup for conducting the process in the diagram above. What would you have to do to achieve step $34$ along the isothermal path if the cartoon below shows the conditions at position $(3)?$ Hint: Your answer should be as quantitative as possible. For example, rather than writing "remove bricks" write "remove $5$ bricks one by one" or rather than writing "add sand" write "add sand quickly up to the equivalent of two bricks". Explain your answer.