What is the standard gibbs free energy for the transformation of diamond to graphite at 298 k? cdiamondâcgraphite?

Considering; graphite; standard enthalpy = 0 and entropy = 5.740; diamond standard enthalpy = 1.897 and entropy = 2.38.
Using the equation Delta G = Delta H - Temperature (DeltaS)
Delta H = enthalpy sum of products - enthalpy sum of reactants
Which will be; 0 -1.897 = -1.897 kJ/Mol
Delta S is the entropy sum; given by 
5.740 - 2.38 = 3.36 J/Mol
We can convert Delta S from Joules to kilo Joules by dividing by 1000
we get ; 0.00336 kJ/mol
We are given a temperature in kelvin which suits the calculations ((298 k)
Therefore; using the equation; 
= -1.897 - (298 × 0.00336) = -2.90 kJ
Thus; the standard gibbs free energy will be; -2.9 kJ