The graph in Fig. $2$ shows a $pV-$diagram for $3\mathrm{.}25$ moles of ideal helium $($He$)$ gas. Part $ca$ of this process is isothermal. $($a$)$ Find the pressure of the He at point $a.($b$)$ Find the temperature of the He at points $a,b,$ and $c.($c$)$ How much heat entered or left the He during segments $ab,bc,$ and $ca?$ In each segment, did the heat enter or leave? $($d$)$ By how much did the internal energy of the He change from $a$ to $b,$ from $b$ to $c,$ and from $c$ to $a?$ Indicate whether this energy increased or decreased. $(25$ points$)$

e $2$