Heat Transfer in an Isobaric Process

$1)$ A piston$-$cylinder device contains $1$ kg of air at $300$ K and $1$ MPa. The air is heated at constant pressure until its temperature reaches $600$ K$.$ Calculate the heat added to the system, the work done by the air, and the change in internal energy.

$2)$ Discuss the implications of using the constant pressure specific heat $($C$\_$P$)$ in this calculation.