The standard enthalpy of formation of pentane relates to the equation:
                                                                            

C(s) + H2(g) → C5H12(l)

The standard enthalpy changes of combustion for the three substances in the equation are: C(s) = -394 kJ/mol, H2(g) = -286 kJ/mol and C5H12(l) = -3509 kJ/mol.
i. Calculate the standard enthalpy of formation of pentane.
ii. State whether the reaction is exothermic or endothermic.