$3\mathrm{.}85$ As shown in Fig. P$3\mathrm{.}85,$ a piston$-$cylinder assembly whose

piston is resting on a set of stops contains $0\mathrm{.}5$ kg of helium

gas, initially at $100$ kPa and $25C.$ The mass of the piston

and the effect of the atmospheric pressure acting on the

piston are such that a pressure of $500$ kPa is required to raise

it$.$ How much energy must be transferred by heat to the

helium, in kJ$,$ before the piston starts rising? Assume ideal

gas behavior for the helium.

Fig. P$3\mathrm{.}85$