Answer
$\Delta S = -943 J/K$
Work Step by Step
This is an isothermal process where both the reaction will reach equilibrium temperature after some time.
The final mass of ice is
$m_{f(ice)} = \frac{1773g + 227g }{2} = 1000g$
Hence the mass of water that are frozen is $m_{f(water)} = 1000g - 227g = 773g $
Now find the entropy. Since the water released heat into the ice, the sign must be negative to indicate the loss of energy.
$\Delta S = - \frac{(0.773 kg)(333000) J/kg}{273K}$
$\Delta S = -943 J/K$
