for the process, in kJ $.$

$2\mathrm{.}59$ As shown in Fig. P$2\mathrm{.}59,$ a gas contained within a pistoncylinder assembly, initially at a volume of $0\mathrm{.}1$ m $)$ undergoes a constant$-$pressure expansion at $2$ bar to a final volume of $0\mathrm{.}12m^3,$ while being slowly heated through the base. The cliange in internal energy of the gas is $0\mathrm{.}25$ kJ $.$ The piston and cylinder walls are fabricated from heat$-$resistant material, and the piston moves smoothly in the cylinder. The local atmospheric pressure is $1$ bar.

$($a$)$ For the gas as the system, evaluate work and heat transfer, each in kJ$.$

$($b$)$ For the piston as the system, evaluate work and change in potential energy, each in kJ $.$