Answer
$\Delta S = -644.5 J/K$
Work Step by Step
In this isothermal process, the heat energy is
$Q = −mL_v $
$Q = −(0.130 kg)(20.9×10^3 J/kg) $
$Q = −2717 J $
The entropy of this non isolated system is
$\Delta S = \frac{Q}{T} $
The boiling point of helium is 4.216 K
$\Delta S = \frac{−2717 J }{4.216 K} $
$\Delta S = -644.5 J/K$
