The correct answer for the question that is being presented above is this one: "16.728 g."
Given that
ΔHsolid = -5.66 kJ/mol.
This means that 5.66 kJ of heat is released when 1 mole of NH3 solidifies
When 5.57 kJ of heat is released
amount of NH3 solidifies = 5.57/5.66 = 0.984 moles
molar mass of NH3 = 17 g/mole
1 mole of NH3 = 17 g
So, 0.984 moles of NH3 = 17 X 0.984 = 16.728 g