$2\mathrm{.}21.*$ Consider the following three processes:

A A sample of $2$ mol of belium gas is isothermally and reversibly expanded from a volume of $10$ L and a temperature of $400K$ to a volume of $40L.$

$(2)$ The same sample is reversibly cooled at a constant volume of $10L$ from $400K$ to a temperature of $300K,$ then expanded reversibly and isothermally to a volume of $40L,$ and then heated reversibly from $300K$ to $400K$ at a constant valume of $40L.$

$(3)$ The same sample is expanded irreversibly and isothermally at a temperature of $400K$ from a volume of $10L$ to a volume of $40L$ with a constant external pressure of $1$atm. Calculate $U,q,$ and $w$ for each process.