A piston$-$cylinder assembly count $1$Kg of air within closed system. The air undergoes a power

cycle consisting of these four processes.

$1-2$: isothermal expansion at T$1=600$k from P$1=0\mathrm{.}5$ Mpa to P$2=0\mathrm{.}4$ Mpa.

$2-3$: Isentropic expansion to P$3=0\mathrm{.}3$ Mpa

$3-4$: Isobaric compression to V$4=$V$1$

$4-1$: Isochoric heat addition to initial state.

a$)$ Draw the cycle in p$-$v and T$-$s diagram. $[6]$

b$)$ Find thermodynamic efficiency of this cycle.