Answer
$\Delta m=29.77kg$
Work Step by Step
$m_{1}=\frac{P_{1}V_{1}}{RT_{1}}=\frac{600kPa*13m^3}{0.2968\frac{kPam^3}{kgK}*(17+273.15)K}=90.57kg$
$m_{2}=\frac{P_{2}V_{2}}{RT_{2}}=\frac{400kPa*13m^3}{0.2968\frac{kPam^3}{kgK}*(15+273.15)K}=60.80kg$
Then:
$\Delta m=m_{1}-m_{2}=90.57kg-60.80kg=29.77kg$
