$(3$ points$)$

An insulated $7\mathrm{.}9m^3$ rigid tank contains air initially at $300$ K and $192$kPa.$A46$ heater running off a constant $116\mathrm{.}8$ V power source is used to heat the air. The heater is turned on

long enough for the pressure to increase to $384$ kPa $.$

a$)$ How much boundary work is done?

kJ

b$)$ How long must the heater remain on $($accounting for the fact that the specific heat is not constant$)?$

minutes

c$)$ How long must the heater remain on assuming the specific heat is constant at a value taken from $300$ K $?$

minutes