13. Solving a chemistry problem

4. When dissolving 6.4 g of ammonium nitrate (NH4NO3) in 2 liters of water, the temperature of the solution decreased by 0.74 C. If we take the specific heat capacity of the solution to be 4.2 J / g * K, then the standard enthalpy of dissolution of ammonium nitrate is (in kJ /mol)
1)-78
2) -62
3) 20
4) 62
5) 78